Dna sequence modification-based gene drive

ABSTRACT

Described herein are embodiments relating to manipulation of populations and sex ratio in populations through DNA sequence modifications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application 62/755,763 filed on Nov. 5, 2018, which is hereby incorporated by reference in its entirety.

REFERENCE TO ELECTRONIC SEQUENCE LISTING

The present application is being filed along with an Electronic Sequence Listing. The Electronic Sequence Listing is provided as a file entitled CALTE135ASEQLIST.txt which is 83,105 bytes in size, created on Oct. 31, 2019. The information in the Electronic Sequence Listing is incorporated herein by reference in its entirety.

BACKGROUND Field

The disclosure is generally related to DNA sequence modification-based modification of a population.

Description of the Related Art

Gene drive occurs when genetic elements—including genes, gene complexes, entire chromosomes and endosymbiotic bacteria—are transmitted to viable, fertile progeny at rates greater than those due to Mendelian transmission, resulting in an increase in their frequency in the population over time, even if their presence results in a fitness cost to carriers.

SUMMARY

In some embodiments, a two-vector system is provided. The two-vector system comprises a first vector comprising a DNA sequence modifying enzyme; a first promoter operably linked to the DNA sequence modifying enzyme, wherein the DNA modifying enzyme modifies an endogenous copy of an essential gene; and a second vector comprising a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.

In some embodiments, a two-vector system is provided. The two-vector system comprises a first vector comprising a first sequence encoding a first component of a DNA sequence modifying complex; a second sequence encoding a second component of the DNA sequence modifying complex; a first promoter operably linked to the first sequence encoding the first component; a second promoter operably linked to the second sequence encoding the second component, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene; and a second vector comprising a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.

In some embodiments, the two-vector system comprises a first vector comprising a first sequence encoding a first component of a DNA sequence modifying complex, a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences; and a second vector comprising a second sequence encoding a second component of the DNA sequence modifying complex; a second promoter operably linked to the second component of the DNA sequence modifying complex, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene. In some embodiments of the two-vector system, the first vector comprises the second sequence encoding the second component of the DNA sequence modifying complex, and the second vector comprises the first sequence encoding the first component of a DNA sequence modifying complex.

In some embodiments of the two-vector system, the two vectors are configured to be positioned on a single chromosome or a single extrachromosomal element at a distance from each other, two different chromosomes, a chromosome and an extrachromosomal element, or two different extrachromosomal elements. In some embodiments of the two-vector system, the distance is less than 50 map units.

In some embodiments of the two vector system, the DNA sequence modifying enzyme comprises a nuclease, a base editor, or a Search and Replace Prime editor.

In some embodiments of the two-vector system, the two components of the DNA sequence modifying complex comprise a nuclease, a base editor, or a Search and Replace Prime editor.

In some embodiments of the two-vector system, the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene.

In some embodiments of the two-vector system, the one or more double strand breaks are repaired to create an altered sequence of the essential gene.

In some embodiments of the two-vector system, the base editor creates one or more base changes in endogenous copy of the essential gene to create an altered sequence of the essential gene.

In some embodiments of the two-vector system, the one or more base changes comprise one or more point mutations in the endogenous copy of the essential gene.

In some embodiments of the two-vector system the Search and Replace Prime editor creates base changes, insertions or deletions in the endogenous copy of the essential gene to create an altered sequence of the essential gene.

In some embodiments of the two-vector system, the rescue transgene is either a recoded copy of the essential gene or is a gene of unrelated sequence, wherein the rescue transgene encodes a protein that is functionally equivalent to a protein encoded by the essential gene, and wherein the DNA sequence modifying enzyme does not modify the rescue transgene.

In some embodiments of the two-vector system, the chromosome is an autosome, X chromosome, Y chromosome, Z chromosome, W chromosome, a prokaryotic genome, or supernumerary chromosome.

In some embodiments of the two-vector system, the extra-chromosomal element is a plasmid or a virus.

In some embodiments of the two-vector system, the one or more cargo sequences comprise a one or more foreign gene sequences, or one or more alleles of an endogenous chromosomal or extra-chromosomal gene to which one of the vectors has been linked through nearby insertion on the chromosome or extra-chromosomal element that carries the endogenous allele of interest.

In some embodiments of the two-vector system, the first, second and rescue transgene promoters are selected from the group consisting of a germline promoter, a male specific germline promoter, a female specific germline promoter, a cell-type specific promoter, a tissue-specific promoter, a ubiquitous promoter, a promoter activated at a specific stage of mitosis, a promoter activated at a specific stage of meiosis, a viral promoter or prokaryotic promoter.

In some embodiments, a method of reversibly modifying a population is described. In some embodiments, the method comprises obtaining a wild type organism, positioning a two-vector system in the wild type organism thereby generating an altered organism, generating a further altered organism by inducing one or more sequence modifications in an essential gene by a DNA sequence modifying complex in the two-vector system that result in a defect in survival, growth control, fertility, or differentiation in one or more cells in the organism, and rescuing the defect in survival, growth control, fertility, or differentiation by a rescue transgene in the two-vector system, introducing the altered organism in an environment wherein an increase in a frequency of the altered organism is desired relative to a frequency of the wild type organism in a population; replacing the wild type organism with the altered organism in the population in the environment, thereby obtaining a modified population, reintroducing the wild type organism in an environment wherein an increase in a frequency of the wild type organism is desired relative to a frequency of the modified organism in the modified population; replacing the modified organism with the wild type organism in the modified population in the environment, thereby reversibly modifying the population.

In some embodiments of the method, the one or more cells comprise somatic cells, germline cells, gametes, or a combination thereof.

In some embodiments of the method, the altered organism is heterozygous or homozygous for one or both of the vectors.

In some embodiments of the method, the organism is haploid, diploid, or polyploid.

In some embodiments of the method, the reversible modification of the population occurs at a rapid rate, high frequency, or both. In some embodiments of the method, the rapid rate is defined as replacement of at least 90% of the wild type organism by the altered organism or vice versa in the population after at most 100 generations. In some embodiments of the method, the high frequency is defined as replacement of at least 90% of the wild type organism by the altered organism or vice versa after 100 generations in the population.

In some embodiments, a two-vector system is provided. The two-vector system comprises a first vector comprising a DNA sequence modifying enzyme; a first promoter operably linked to the DNA sequence modifying enzyme, wherein the DNA modifying enzyme modifies an endogenous copy of an essential gene; and a second vector comprising a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.

In some embodiments, a two-vector system is described. In some embodiments the two-vectors system comprises a first vector comprising a first sequence encoding a first component of a DNA sequence modifying complex; a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene; and a second sequence encoding a second component of a DNA sequence modifying complex; a second promoter operably linked to the second sequence encoding the second component of the DNA sequence modifying complex; and a second vector comprising: a rescue transgene sequence and; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.

In some embodiments, a two-vector system is described. In some embodiments, the two-vector system comprises a first vector comprising a first sequence encoding a first component of a DNA sequence modifying complex, a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex; and a second vector comprising a second sequence encoding a second component of a DNA sequence modifying complex; a second promoter operably linked to the second sequence encoding the second component of the DNA sequence modifying complex, a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences, wherein the DNA active modifying enzyme complex modifies an endogenous copy of an essential gene.

In some embodiments, a vector is provided. The vector comprises: a first sequence encoding a first component of a DNA sequence modifying complex; a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex; a second sequence encoding a second component of a DNA sequence modifying complex; a second promoter operably linked to the second sequence encoding complex; a rescue transgene; a promoter operably linked to the rescue transgene that requires binding by the DNA sequence modifying complex for transcription of the rescue transgene; and optionally one or more cargo sequences.

In some embodiments, a two-vector system is provided that comprises: a first vector. The first vector comprises: a first sequence encoding a first component of a DNA sequence modifying complex; a second sequence encoding a second component of the DNA sequence modifying complex; a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex, a second promoter operably linked to the second sequence encoding the second component of the DNA sequence modifying complex. The DNA modifying enzyme complex modifies an endogenous copy of an essential gene. The system comprises a second vector that comprises a rescue transgene sequence; a promoter operably linked to the rescue transgene that requires binding by the DNA sequence modifying complex for transcription of the rescue transgene; and optionally, one or more cargo sequences.

In some embodiments a two-vector system is provided that comprises a first vector that comprises a first sequence encoding a first component of a DNA sequence modifying complex, a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex, a rescue transgene sequence; a promoter operably linked to the rescue transgene that requires binding by the DNA sequence modifying complex for transcription of the rescue transgene; and optionally, one or more cargo sequences. The two-vector system further comprises a second vector that comprises a second sequence encoding a second component of the DNA sequence modifying complex; and a second promoter operably linked to the second component of the DNA sequence modifying complex. The DNA modifying enzyme complex modifies an endogenous copy of an essential gene. In some embodiments, the first vector comprises the second sequence encoding the second component of the DNA sequence modifying complex, and the second vector comprises the first sequence encoding the first component of a DNA sequence modifying complex.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-FIG. 1C show an embodiment of an X cleavage mediated Y drive. The vector is present on the Y chromosome. Cleavage of an essential gene located on the X chromosome is brought about by Cas9 and associated gRNAs. The Y chromosome also carries a recoded version of the essential gene that is resistant to cleavage by Cas9.

FIG. 1A shows a schematic of the mechanism of action an embodiment of a vector (transgenic construct) that brings about drive of a vector-bearing Y chromosome through cleavage of an essential gene on the X chromosome.

FIG. 1B shows a schematic of an embodiment of inheritance, and viable or non-viable progeny, of an X chromosome cleavage mediated Y chromosome drive process. X (linear) and Y (kinked) chromosomes are indicated.

FIG. 1C shows a graph of an embodiment of a population frequency modeling of X cleavage mediated Y drive for different fitness costs and introduction frequencies. The heat map to the right indicates the number of generations required for the vector to reach a population frequency of >99%.

FIG. 2A-FIG. 2C show an embodiment of a cleavage mediated X drive with the vector also located on the X.

FIG. 2A shows a schematic of the mechanism of action an embodiment of a vector (transgenic construct) for cleavage mediated X drive with the vector located on the X.

FIG. 2B shows a schematic of inheritance, and viable or non-viable progeny, of a cleavage mediated X drive process with the vector located on the X.

FIG. 2C shows a graph of an embodiment of a population frequency modeling of cleavage mediated X drive with the vector located on the X.

FIG. 3A-FIG. 3C show an embodiment of a cleavage mediated autosomal drive.

FIG. 3A shows a schematic of the mechanism of action an embodiment of a vector (transgenic construct) for cleavage mediated autosomal drive.

FIG. 3B shows a schematic of inheritance and viable or non-viable progeny of a cleavage mediated autosomal drive process.

FIG. 3C shows a graph of an embodiment of a population frequency modeling of cleavage mediated autosomal drive.

FIG. 4A-FIG. 4C show an embodiment of a cleavage mediated 2-locus autosomal drive.

FIG. 4A shows a schematic of the mechanism of action an embodiment of a vector (transgenic construct) for cleavage mediated 2-locus autosomal drive.

FIG. 4B shows a schematic of inheritance, and viable or non-viable progeny, of a cleavage mediated 2-locus autosomal drive process.

FIG. 4C shows a graph of an embodiment of a population frequency modeling of cleavage mediated 2-locus autosomal drive.

FIG. 5A-FIG. 5C show an embodiment of a cleavage mediated haplolethal drive.

FIG. 5A shows a schematic of the mechanism of action an embodiment of a vector (transgenic construct) for cleavage mediated haplolethal drive.

FIG. 5B shows a schematic of inheritance and viable or non-viable progeny of a cleavage mediated haplolethal drive process.

FIG. 5C shows a graph of an embodiment of a population frequency modeling of cleavage mediated haplolethal drive.

FIG. 6A-FIG. 6F show a schematic of an embodiment of maintenance of extrachromosomal element.

FIG. 7 shows a schematic of an embodiment the results of a cross between a female insect heterozygous for the vector with germline expression of the DNA sequence modifying enzyme and a wild type male when there is no carryover of DNA cleavage/alteration activity from germline into embryo.

FIG. 8A shows a schematic of an embodiment the results of a cross between an insect heterozygous for the vector with germline expression of the DNA sequence modifying enzyme an a second insect heterozygous for the vector when there is no maternal transfer of DNA cleavage/alteration activity from germline into embryo. Individuals that inherit no functional copies of the essential gene die, while those that inherit at least one copy of the vector and its associated rescue transgene survive.

FIG. 8B shows a graph of an embodiment of vector-mediated gene drive/population replacement for an autosomal two locus scenario, with different fitness costs and introduction frequencies, and without maternal transfer of DNA cleavage/alteration activity.

FIG. 9A shows a schematic of an embodiment the results of a cross when there is maternal transfer of DNA cleavage/alteration activity from germline into embryo.

FIG. 9B shows a graph of an embodiment of vector-mediated gene drive/population replacement for different fitness costs and introduction frequencies with maternal transfer of DNA cleavage/alteration activity.

FIG. 10 shows a schematic of an embodiment of a meiotic gene drive. Spores that fail to inherit a functional copy of the essential gene die.

FIG. 11 shows a schematic of an embodiment of vector-mediated sex ratio distortion.

FIG. 12 shows a schematic of an embodiment of homing endonuclease gene (HEG)-based population replacement in which the cargo gene is included as a component of the HEG

FIG. 13 shows a schematic of an embodiment of HEG-based population replacement in which the cargo is located at a different site in the genome.

FIG. 14 shows a schematic of an embodiment of a Medea-based gene drive.

FIG. 15A-FIG. 15C show an embodiment of DNA sequence modification based gene drive (herein referred to as ClvR when a nuclease is used for DNA sequence modification) construct design and principle according to the present disclosure.

FIG. 16A-FIG. 16B show an embodiment of a determination of the effects of a CleaveR drive when transmitted through the female (FIG. 16A) or male (FIG. 16B) germline.

FIG. 17 shows an embodiment of an alignment of the target gene (Drosophila melanogaster tko—Examples 15 and 16) with the recoded rescue based on Drosophila virilis tko. PAM in bold letters, additional silent point mutations introduced into the rescue copy to reduce homology also indicated by shading.

FIG. 18A show a schematic of an embodiment of the components of the DNA sequence modification-based gene drive (Example 17).

FIG. 18B shows a schematic of an embodiment of the components of the step 1 of FIG. 18A (Example 17).

FIG. 18C shows a schematic of an embodiment of the components of the step 2 of FIG. 18A (Example 17).

FIG. 19 shows an embodiment of the results of Sanger sequencing from the endogenous tko locus following cleavage by Clv^(tko), demonstrating LOF allele creation, from Example 17.

FIGS. 20A-D show schematics of embodiments of single locus ClvR, and two locus ClvR involving components located on two separate chromosomes.

FIG. 20A shows schematics of embodiments of single locus ClvR.

FIG. 20B shows schematics of embodiments of two locus ClvR, version 1.

FIG. 20C shows schematics of embodiments of two locus ClvR, version 2.

FIG. 20D shows schematics of embodiments of two locus ClvR, version 3.

FIGS. 21A-C show schematics of embodiments of two locus ClvR involving components located on the same chromosome at a distance of less than 50 map units.

FIG. 21A shows schematics of embodiments of two locus ClvR, version 1, involving components located on the same chromosome at a distance of less than 50 map units.

FIG. 21B shows schematics of embodiments of two locus ClvR, version 2, involving components located on the same chromosome at a distance of less than 50 map units.

FIG. 21C shows schematics of embodiments of two locus ClvR, version 2, involving components located on the same chromosome at a distance of less than 50 map units.

FIG. 22 shows a schematic of an embodiment of ClvR in which the Cargo transgene is located in an intron of the Rescue transgene. Similar considerations apply to two locus versions also.

FIG. 23 shows a schematic of an embodiment of ClvR in which the cargo is located between two transgenes whose co-expression is required to create a functional Rescue protein. Similar considerations apply to two locus versions also.

FIG. 24 shows a schematic of an embodiment of ClvR in which the Rescue and the Cargo transgenes are arranged such that the Cargo is located between two transgenes, the presence of both of which is required for expression of a functional Rescue transgene. Similar considerations apply to two locus versions also.

FIG. 25 shows a schematic illustrating how ClvR can create loss of function (LOF) alleles using homologous recombination.

FIG. 26 shows a schematic illustrating how movement of the site-specific DNA modifying enzyme between cells can result in selection for ClvR-bearing genotypes.

FIG. 27 shows a schematic of the second step construct for ClvR^(tf2a). Sequence is listed in file labeled tf2a-step2-sequence. Sequence of step 1 Drosophila suzukii Rescue transgene is listed in sequence file tf2a-suzukii-melanogaster-alignment.

FIG. 28 shows a schematic of the second step construct for ClvR^(dbe). Sequence is listed is file labeled dribble2-s2-sequence. Sequence of step 1 Drosophila suzukii Rescue transgene and alignment with Drosophila melanogaster sequence is in sequence file dribble-Dsuz-swFB-BLASTN.

FIGS. 29A-D show data from example 17 illustrating drive to genotype fixation in Drosophila for ClvR^(tko).

FIG. 29A shows data from 5 drive experiments in which heterozygous ClvR-bearing males were crossed with wildtype females in generation zero.

FIG. 29B shows data from 4 drive experiments in which equal numbers of homozygous ClvR-bearing males and wildtype males were crossed with wildtype females in generation zero.

FIG. 29C shows data from 4 control drive experiments in which males heterozygous for the step 1 construct, which carries only the Rescue transgene, were crossed with wildtype females in generation zero.

FIG. 29D shows data from the 5 drive experiments from FIG. 29A showing the fraction of individuals who are homozygous for ClvR^(tko).

FIG. 30 shows data from example 17 (upper panels) and example 24 (middle and lower panels), illustrating drive to genotype fixation in Drosophila for ClvR^(tko) (upper left panels), ClvR^(tf2a) (lower left panels) and ClvR^(dbe) (middle left panels), but not of the control constructs (right panels).

FIGS. 31A-D show graphs of an embodiment of a population frequency modeling of cleavage mediated drive for genes that are haploinsufficient or haplolethal.

FIG. 31A shows a graph of an embodiment of a population frequency modeling of single locus ClvR drive targeting a haplosufficient locus without maternal carryover for different fitness costs.

FIG. 31B shows a graph of an embodiment of a population frequency modeling of single locus ClvR drive targeting a haplosufficient locus with maternal carryover for different fitness costs

FIG. 31C shows a graph of an embodiment of a population frequency modeling of single locus ClvR drive targeting a haploinsufficient locus with maternal carryover for different degrees of haploinsufficiency

FIG. 31D shows a graph of an embodiment of a population frequency model of single locus ClvR targeting a haplolethal locus for different introduction frequencies.

FIG. 32 shows a schematic illustrating a strategy by which Cas9, gRNAs and Rescue transgene can be implemented such that Cas9 and gRNAs are required for Rescue expression in addition to cleavage of an essential gene.

FIG. 33 shows schematics illustrating how second generation ClvR elements can be used to replace first generation elements when both are located at the same position in the genome. Upper panel shows general strategy. Lower panel shows schematics illustrating how a specific implementation is created using components from Example 17 and Example 24.

FIGS. 34A-34F show graphs of an embodiment of a population frequency modeling of two locus ClvR, version 1, including reversibility through dilution of an altered population with wildtpes.

FIGS. 35A-35F show graphs of an embodiment of a population frequency modeling of two locus ClvR, versions 2 and 3, including reversibility through dilution of an altered population with wildtypes.

FIG. 36 shows graphs of an embodiment of a population frequency modeling of single locus ClvR, including lack of reversibility through dilution of an altered population with wildtypes under conditions present in FIGS. 34A-F and FIGS. 35A-F.

FIG. 37 shows an embodiment of an alignment of amino acid sequence of D. virilis tko (Dvir-Tko-aa) and the two annotated protein isoforms from D. melanogaster (Dm-Tko-aa-B and Dm-Tko-aa-C).

FIG. 38A-FIG. 38D show another embodiment of the ClvR construct design and principle from Example 17.

FIG. 38A shows Construct A with a U6:3-gRNA, an attP site, the tko rescue copy based on Drosophila virilis tko and a ubiquitous opie2-td-tomato marker. Only elements between the homology arms were inserted into a neutral site (68E) on the 3rd chromosome via Cas9 mediated HR. Cloning primers for Gibson assembly are indicated as arrows.

FIG. 38B shows Construct B with an attB site, a 3×P3-GFP marker, Cas9 driven by nanos regulatory elements, and a set of four U6 driven gRNAs. Construct B was integrated into the attP landing site of construct A via phiC31 integrase.

FIG. 38C shows final construct after B was integrated into A.

FIG. 38D shows principle by which ClvR acts. Females heterozygous for the ClvR construct create cleaved and LOF tko alleles in the germline. Additionally, active Cas9/gRNA complex is deposited maternally to all embryos, where subsequently paternal alleles are cleaved rendered LOF. Offspring without the Rescue copy from the ClvR element die.

FIG. 39A-FIG. 39C show embodiments of Mating scheme to isolate X chromosomes in which the D. melanogaster tko locus was not rendered non-functional (escapers) in the germline of male parents heterozygous for Clv^(tko).

FIG. 39D-FIG. 39E shows embodiments of sequencing alignments to target sites 1,2 FIG. 39D) and 3,4 (FIG. 39E). Escaper “escF1” from bottle 2 of female ClvR^(tko)/+XXw¹¹¹⁸ (see TABLE 4). Escapers M1-M3 from bottle 1, M4-M8 from bottle 2 of male Clvk^(tko) XX tko³/FM7,B¹ (see TABLE 5). Male escapers from bottle 2 have a common SNP (G to A between gRNA1 and gRNA2) not present in escapers from bottle 1. Thus, it is possible that the 8 isolates from males represent multiple isolates of two or more germline events. Note that the large number of sequence polymorphisms in escM3A and escM3B reflects ambiguous sequencing signal at a variety of positions. The basis for this remains unclear. Without being limited by any particular theory, it is speculated that this reflects nuclear mosaicism, which could occur if the F1 ClvR^(tko)-bearing males provided some level of paternal carryover that altered the tko locus from the Xp chromosome in some nuclei of the F2 males used for sequencing and crosses to the ClvR^(tko)-bearing female.

FIG. 40A-FIG. 40D show embodiments of molecular analysis of cleavage events that result in LOF of Drosophila melanogaster tko. Shown are the alignments of the tko locus of male progeny coming from Clvk^(tko)/+ mothers (two flies selected from 9 crosses, tko1A, tko1B, . . . tko9B) (FIG. 40A & FIG. 40B) or from a homozygous stock inbred for 3 generations (12 flies selected from bottles, tkoG3-1 to tkoG3-12) (FIG. 40C & FIG. 40D). Alignments were split for ease of visibility. gRNA1 and gRNA2 target sites are show in FIG. 40A and FIG. 40C, and gRNA3 and gRNA4 target sites in FIG. 40B and FIG. 40D. Top row shows the template with annotated gRNA target sites and amino acid sequence. Mismatches in the alignments are shown.

FIG. 41 shows an embodiment of removal of a first generation ClvR, coupled with replacement by a second generation ClvR element. Multiple rounds of population replacement can be carried out by locating ClvR^(n+1) at the same site as ClvR^(n), with ClvR^(n+1) targeting essential gene^(n+1), while also carrying the original rescuing copy of essential gene^(n). Because progeny carrying ClvR^(n) are sensitive to loss of essential gene^(n+1), only those carrying ClvR^(n+1) survive, regardless of their status with respect to ClvR^(n). The function of ClvR^(n+1) can be made completely orthogonal to that of ClvR^(n) through the use of Cas9/gRNA variants from other species that cannot load the gRNAs generated by ClvR^(n).

FIG. 42A-FIG. 42C show an embodiment from Example 17 of components of ClvR and its behavior in females and males.

FIG. 42A shows component genes and their arrangement in ClvR^(tko).

FIG. 42B shows an embodiment of the behavior of ClvR^(tko) when present in a ClvR^(tko)/+adult female. Female progeny inherit an X from their mother and one from their father. Male progeny inherit an X from their mother. One non-ClvR^(tko)-bearing male survived. 3735 surviving progeny inherited ClvR^(tko), for a cleavage rate of >99.9%.

FIG. 42C shows an embodiment of the behavior of ClvR^(tko) when present in a ClvR^(tko)/+ male. When ClvR^(tko)/+ males are crossed to tko³/FM7,B¹ females, non-FM7,B¹ female progeny carry tko³ and an X chromosome from their father. 907 of these carry ClvR^(tko), while only 8 (which may not represent independent events; FIGS. 39A-E and TABLE 5) do not, for a cleavage rate of >99%. Individuals carrying the FM7,B¹ balancer, particularly males, are much less fit than others, and were not considered in the calculations. ClvR^(tko)-dependent rescue of the tko³ mutant phenotype is indicated by the large numbers of tko³/Y; ClvR^(tko)/+ progeny (880), as compared with none for tko³/Y; +/+.

FIG. 43 illustrates some embodiments in which cells that acquire a competitor plasmid are eliminated if this results in the loss of the ClvR-bearing plasmid.

FIG. 44 depicts a sequence of some embodiments.

FIG. 45 depicts a sequence of some embodiments.

FIG. 46 depicts a sequence of some embodiments.

FIG. 47 depicts a sequence of some embodiments.

FIG. 48 depicts a sequence of some embodiments.

FIG. 49A shows schematic showing embodiments of the genetic constructs used to create two locus ClvR in Drosophila. On chromosome 2 (identified by the 2 in a circle), the Cleaver locus contains Cas9, whose expression is driven by the nanos promoter and the dominant marker td-tomato, all integrated using a site-specific recombination system (attL and attR). On chromosome 3 (identified by the 3 in a circle) the Rescue+Cargo+gRNAs and their insertion site are derived from the single locus ClvR system described by Oberhofer et al., (2019). However, Cas9 activity has been eliminated (Xs).

FIG. 49B shows an embodiment of population dynamics of components of a two locus ClvR system in Drosophila, in four replicates. Version 3, as illustrated in FIG. 20D, is implemented. Rescue, gRNAs and Cargo are present on the third chromosome. Cas9 is on the second chromosome, and the target locus, tko, is on the X. Rescue and Cargo are found in two different populations of individuals, as is Cas9. See example X.

FIG. 49C shows an embodiment of population dynamics of components of a two-locus ClvR system in Drosophila, in four replicates. Version 3, as illustrated in FIG. 20D, is implemented. Rescue, gRNAs and Cargo are present on the third chromosome. Cas9 is on the second chromosome, and the target locus, tko, is on the X. Rescue and Cargo are ultimately found in almost all individuals in the population. In contrast, the frequency of Cas9-bearing individuals decreases over time.

FIG. 49D shows an embodiment of dynamics of components of a two-locus ClvR system in Drosophila, in four replicates. Version 3, as illustrated in FIG. 20D, is implemented. Data is from FIG. 49A and FIG. 49B. Rescue, gRNAs and Cargo are present on the third chromosome. Cas9 is on the second chromosome, and the target locus, tko, is on the X.

FIG. 49E shows an embodiment of individual replicates of the four drive experiments illustrated in FIGS. 49B-49D.

FIG. 50 shows an embodiment of modeling of two locus ClvR with linkage and different levels of recombination between the two loci.

DETAILED DESCRIPTION

In nature gene drive is brought about by a number of mechanisms, in a number of contexts (Ben-David et al. 2017; Burt and Trivers 1998; Seidel et al. 2011; Nuckolls et al. 2017; Hu et al. 2017). A number of novel methods of engineering gene drive have also been proposed, and in several cases implemented.

There are two general contexts in which gene drive is considered as a technological tool. In one, the goal is population replacement: to spread a trait throughout an extant population. This is sometimes also referred to as population alteration. Herein these terms are used interchangeably. For organisms such as beneficial insects such traits include insecticide, natural pathogen resistance or resistance to other stresses. For a pest/disease vector traits of interest include insecticide sensitivity, the inability to carry or transmit specific pathogens, or a change in life history that preclude pathogen transmission. Genes that confer conditional lethality in response to an environmental cue, so as to ultimately bring about population suppression, are also of interest. A second goal is population suppression or elimination. Targets of interest include invasive species of plants and animals, pests that cause damage directly to plants or animals, and vectors of plant or animal disease. Finally, gene drive is also of interest as a tool for maintaining the presence of a trait in a population in which the genetic element (plasmid, chromosome, virus) in which the gene drive element and any associated cargo genes are sometimes lost, for example during cell division. This is related to population replacement.

A number of methods have been considered for bringing about self-sustaining population replacement. Many of these take as their starting point naturally occurring selfish genetic elements to which cargo genes could be linked (Braig and Yan 2001; Burt and Trivers 1998; Chen et al. 2007). Others involve the use of novel, engineered systems, many of which utilize, in one way or another, the phenomenon of underdominance (heterozygote disadvantage) (Gould and Schliekelman 2004; Marshall and Hay 2011; Marshall and Hay 2012; Marshall et al. 2011; Akbari et al. 2013; Altrock et al. 2010; Altrock et al. 2011; Davis et al. 2001; Gokhale et al. 2014; Reeves et al. 2014). An important characteristic of any gene drive mechanism is its level of invasiveness: its ability to increase in frequency both at the point of release and in surrounding areas linked to the release site by various levels of migration, when introduced at various population frequencies. Here, gene drive mechanisms are divided somewhat arbitrarily into low and high threshold variants, with the understanding that these distinctions lie along a continuum. Low threshold gene drive mechanisms require that only a small fraction of individuals in the population carry the drive element in order for spread to occur locally (Marshall 2009; Marshall and Hay 2012). Examples include transposons, engineered Medea chromosomal elements (Chen et al. 2007; Wade and Beeman 1994; Ward et al. 2011), several other possible single locus chromosomal elements (Marshall and Hay 2012), site-specific nucleases that home into their target site (Burt 2003; Gantz and Bier 2015; Gantz et al. 2015; Hammond et al. 2016; Simoni et al. 2014; Windbichler et al. 2011), and site-specific nucleases located on the Y chromosome that cleave and thereby (somehow) block development of X-bearing sperm, resulting in sex ratio distortion (Galizi et al. 2014). These mechanisms are predicted to be invasive because low levels of migration of drive element-bearing individuals into areas outside the release area may, depending on the threshold and the migration rate (Beaghton et al. 2016; Beaghton et al. 2017; Godfray et al. 2017; Marshall 2009; Marshall and Hay 2012), result in these areas being seeded with enough transgene-bearing individuals that drive is likely to occur. Low threshold, invasive gene drive mechanisms are attractive when the goal is to spread transgenes over a large area, and migration rates between the release site and surrounding areas of interest are low. However, for these same reasons, it is likely to be challenging to restore the population to the pre-transgenic state if desired. High (or higher) threshold gene drive mechanisms require, as their name implies, that transgenes make up a much larger fraction of the total insect population (important examples range from ˜15-70%) before gene drive occurs. Below this frequency transgenes are instead actively eliminated from the population. These drive mechanisms thus behave as frequency-dependent bistable switches. High transgene frequencies are needed to initiate drive at the release site, limiting the possibility that unintended release of a few individuals could initiate replacement (Marshall 2009). Furthermore, once replacement has occurred at the release site, spread to high frequency in areas connected to the release site by low levels of migration is prevented because the transgene never reaches the threshold frequency needed for drive (Altrock et al. 2010; Altrock et al. 2011; Marshall and Hay 2012). Finally, transgenes can be eliminated from the population if the release of wildtypes results in the frequency of transgenics being driven below the threshold required for drive. A number of gene drive mechanisms that could in principal bring about high threshold gene drive have been proposed. Examples include a number of single locus toxin-antidote gene drive mechanisms (Marshall and Hay 2011; Marshall and Hay 2012; Marshall et al. 2011), reciprocal chromosome translocations, inversions and compound chromosomes (Gould and Schliekelman 2004), and several forms of engineered underdominance (Akbari et al. 2013; Altrock et al. 2010; Altrock et al. 2011; Davis et al. 2001; Gokhale et al. 2014; Marshall and Hay 2012; Reeves et al. 2014). Two of these, UD^(MEL) (double Medea), and engineered reciprocal translocations, have recently been shown to drive reversible population replacement into populations of wildtype Drosophila (Akbari et al. 2013; Buchman et al. 2018). A third system has been shown to drive high threshold population replacement in Drosophila in a split configuration (Reeves et al. 2014). In each of these systems gene drive occurs when transgene-bearing chromosomes experience frequency-dependent changes in fitness with respect to non-transgene-bearing counterparts, with the former having high fitness at high frequency and lower fitness at low frequency. These systems all rely, in one way or another, on the phenomena of underdominance, in which transgene-bearing heterozygotes (or some fraction of them or their progeny) have a lower fitness than either homozygous wildtypes or homozygous transgenics (or transgene-bearing trans-heterozygote in some three allele cases). If the frequency of one allele or pair of alleles or chromosome type is above a critical threshold it spreads to genotype, and in some cases allele fixation. Conversely, if it falls below the critical threshold it is lost in favor of the other allele or chromosome type, usually wildtype. In broad outline, this behavior occurs because when transgene-bearing individuals are common they mate mostly with each other, producing transgene-bearing offspring of high fitness (high survival and/or fecundity), while wildtypes mate mostly with transgene-bearing individuals, producing a preponderance of heterozygous offspring of low fitness (inviable and/or with reduced fecundity). However, when the frequency of wildtypes is high the tables are turned, with transgene-bearing individuals producing high frequencies of unfit heterozygous progeny, and wildtypes producing a high frequency of fit homozygous progeny.

The only gene drive mechanisms shown to drive population replacement in otherwise wildtype organisms are Medea (Akbari et al. 2012; Buchman et al. 2018; Chen et al. 2007), UDMEL (double Medea) (Akbari et al. 2013), and reciprocal chromosome translocations (Buchman et al. 2018), all in Drosophila melanogaster or Drosophila suzukii. Several other methods, including engineered underdominance (Reeves et al. 2014) and homing endonucleases (Windbichler et al. 2011; Windbichler et al. 2007; Simoni et al. 2014; Gantz and Bier 2015; Gantz et al. 2015; Hammond et al. 2016; Champer et al. 2017; Chan et al. 2011; Chan et al. 2013), have seen important progress, though population replacement has not been demonstrated.

There is a need for robust mechanisms of gene drive that can easily be developed for diverse species, and that are robust to mechanisms that can cause failure of gene drive to occur. Thus, while Medea elements have been generated in Drosophila, it has not yet been possible to develop them in other insects. In addition, Medea is inherently challenging because it requires that early zygotic promoters be available, along with antidotes, which together are capable of rescuing maternal lethality. These reagents, as well as specific mechanisms for bringing about toxicity in embryos but not oocytes, are challenging to identify and create, and their implementation requires that one have detailed biological knowledge of the species under consideration (Hay et al. 2010). UDMEL (double Medea) represents a more complicated version of Medea, and therefore suffers from the same problems (Akbari et al. 2013). Homing-based population replacement is challenging for several reasons. First, it requires that DNA cleavage be followed by DNA repair using homologous recombination, and that homologous recombination proceed through the entire gene drive element that must be copied. Since the cell utilizes multiple repair pathways, and HR is inefficient, complete copying through HR often does not happen. Second, because homing requires the targeting and cleavage of a specific sequence, its efficacy is sensitive to genomic sequence variation. Variation can occur as pre existing sequence polymorphisms in a population. It can also arise from mutation, and as a result of break repair through non-homologous end joining, which is error prone (Preston et al. 2006; Windbichler et al. 2011). Regardless of the mechanism, sequence variants that are not cleaved are resistant to homing, and may retain some or complete wildtype gene function. The presence of such resistant alleles can block HEG spread and thereby prevent population replacement. Thus, the question of how to bring about high frequency homing that is gene specific, but insensitive to some level of sequence variation within the gene, is central to the development of HEG-based population replacement technologies, and remains to be solved. Translocations can only provide high threshold population replacement. They also require a significant amount of chromosomal engineering, in that two large chromosome fragments must become linked to each other, while maintaining high levels of organism fitness (Buchman et al. 2018; Marshall and Hay 2012). Finally, shredding of the X chromosome through the use of a P-linked transgene that thereby causes the loss of X-bearing sperm has also been proposed (Burt 2003), and significant progress has been made (Galizi et al. 2014; Galizi et al. 2016; Windbichler et al. 2008). However, this approach is limited to population suppression and species that have clear X and Y chromosomes in which males are Y. Many species of interest lack this configuration. In summary, gene drive for population replacement is an important technological goal, but methods for easily engineering it in diverse species are lacking.

As a specific example of the need for population replacement gene drive, despite a myriad of approaches to controlling mosquito-borne infections, ranging from insecticide treated bed nets, new anti-malarial drugs such as artemisinin, and suppression attempts using sterile males, there are still over 600,000 deaths from malaria each year [WHO World Malaria Report 2014]. This stems from a combination of lack of human compliance, emerging drug resistance, and selection for mosquitoes preferring to bite outdoors. These failures show the need for novel molecular approaches to combating insect-borne disease [Alphey, 2014].

However, the approaches proposed face substantial barriers to their development. In toxin-antidote systems, the toxin has to be strong enough to suppress one or both copies of the target gene and the recoded ‘antidote’ version of this gene has to have strong enough and timely zygotic expression to compensate for the loss of the maternal product Chen et al 2007, [Akbari, 2013; Akbari, 2014]. These are already difficult requirements for the development of a first generation gene drive, let alone successive drives (second and third generation versions) in case the original mutates to inactivity. Additionally, what works in one species, such as the Medea^(myd88) in Drosophila melanogaster, does not necessarily work in other species, such as Aedes aegypti, despite sharing the molecular components involved in the drive.

HEG approaches are elegant in that they increase their frequency not through the destruction of competing alleles as in toxin-antidote drives but by copying themselves onto non HEG containing homologs, thus forcing heterozygotes for the HEG to become homozygous. However, they suffer from the being limited in what they can target due to their inherent base specificity and from potential replication errors every time they are copied.

HEG based approaches to gene drive are predicted to be very powerful, driving from low frequency and in relatively few generations. The emergence of TALENs and ZFNs have vastly expanded the number of possible target sites while maintaining specificity, but their multiple repeats make them prone to mutation due to recombination [Simoni, 2014; Esvelt, 2014]. An alternative now being very actively explored utilizes the CRISPR nuclease Cas9 and gRNAs that target Cas9 to specific sequences for cleavage based on Watson-Crick base pairing interactions. While HEGs based on Cas9 can target virtually any sequence, a Cas9 drive construct is likely to be quite large, making homing more difficult and the construct much more prone to copying errors.

While drives like Medea can incorporate new toxins in addition to old ones to perform additional stages of replacement, adding additional gRNAs will buffer a Cas9 HEG against NHEJ resistant alleles but will only make the construct even larger and thus more prone to other problems, such as abortive gap repair.

Cas9 and other RNA-guided DNA nucleases can be used at the heart of any of the gene drives previously proposed for use as HEGs, with a substantially larger pool of potential targets while maintaining specificity. However, these strategies have the major drawback of susceptibility to DNA loss or drive dysfunction due to the imperfect copying of Cas9 and any associated cargo during homology directed repair.

As detailed in PCT Application No. PCT/US2018/030990 (the entirety of which is incorporated by reference here), various gene drive systems are known. Some involve a first and second component. The first component is a gene (or genes) expressing an enzyme (or the two essential components of an enzyme) that bring about DNA sequence modification, and thus inactivation (creation of loss of function [LOF] alleles), of an essential gene. The second component is a transgene (the rescue transgene) that is able to rescue the loss of function phenotype due to inactivation of the endogenous copies of the essential gene, and is insensitive to enzyme-mediated DNA sequence modification. This method requires only two components: a site-specific DNA modifying enzyme that targets a gene required for viability or fertility in any way (an essential gene), and a second, functional version of the essential gene that includes sequences that are resistant to modification by the site-specific DNA modifying enzyme (the rescue transgene). When these two elements are linked together, for example, in a vector (e.g., plasmid, chromosome, extrachromosomal element, virus), organisms that carry the vector always survive because they always carry the rescue transgene. In contrast, organisms that do not carry the rescue transgene will die or be sterile if they only carry inactive copies of the essential gene that are inherited from vector-bearing parents or created de novo through site-specific DNA modifying enzyme activity that is brought into these cells through diffusion, transport, or cell-cell movement. The above is taken a step further herein, and involves two or more loci for the embodiments presented in PCT Application No. PCT/US2018/030990. In some embodiments, two locus gene drive is provided herein, and can be applied to any of the single locus embodiments described herein, as outlined herein. That is, any of the embodiments provided herein can be modified such that there are effectively two or more loci in the system. In some embodiments, two vectors (“a two-vector system”) are provided for the implementation of the various embodiments provided herein. Without being limited by any particular theory, the fact that two locus gene drive wanes over generations provides two locus systems (such as ClvR) with three important new, unique features not exhibited by single locus systems (e.g., ClvR embodiments provided herein). As a short hand, embodiments are provided herein with respect to CLvR, however, these embodiments can be employed in the other embodiments provided herein as well (as appropriate).

First, gene drive for a given population introduction frequency is limited in time. This is illustrated, for example in FIGS. 34A-F and FIGS. 35A-F, and FIG. 49A-E, FIG. 50, and illustrated in Example 41 and Example 42, and occurs because the frequency of one or both Cas9/gRNA components decreases over time. Once these alleles are at low frequency or are eliminated, drive can no longer occur. However, even though drive is eliminated, the Rescue/Cargo can remain at genotype fixation. Without being limited by any particular theory, this occurs because all (or nearly all) wildtype alleles of the essential gene have been eliminated, locking the population into a Cargo/Rescue-bearing state.

The second new and unique feature of two locus ClvR is that drive is limited in space. It is local rather than global, as with single locus ClvR. This is because as the transgene-bearing organisms distribute in space from a source through migration, the frequency of the Cas9/gRNA components will decrease. Drive of the Cargo/Rescue only occurs in which the frequency of Cas9/gRNA (or that of other RNA-guided DNA sequence modifying enzymes such as base editors or Prime editors) is high enough to bring about high frequency creation of LOF alleles of the essential gene. In particular, when two locus ClvR individuals are migrating into a neighboring population composed mostly of wildtypes, the independent segregation of the two chromosomes means that Cas9/gRNA-bearing individuals will often find themselves without a copy of the Rescue, and therefore die. In the absence of levels of LOF allele creation sufficient to create many LOF homozygotes, drive of the Cargo/Rescue into the population will not occur. These points are illustrated in FIG. 50, which shows that for a constant introduction frequency the degree of linkage determines the extent of drive, and whether the Rescue and Cargo spread to high frequency.

The third new and unique feature of two locus ClvR is that with it, unlike with single locus ClvR, reversibility to a population that lacks the Cargo/Rescue and the cleaved allele can be achieved by dilution of a transgene-bearing population with wildtype individuals. Whenever the presence of the Cargo/Rescue results in some fitness cost, dilution can lead to elimination of drive, Cargo and LOF alleles of the essential gene, from the population. In contrast, with single locus ClvR, reversibility cannot easily be achieved through dilution because the drive is so powerful. See, for example, FIGS. 34A-F and FIGS. 35A-F. A similar result is implied by the modeling presented in FIG. 50 and the data from Example 40 presented in FIGS. 49A-E.

The above three features are useful to implement in order to have the gene drive mechanisms function within regulatory frameworks. Central to these developments are aspects of confinement and reversibility: can the spread of transgenes to high frequency be limited to locations in which their presence is sought, and can the population be restored to the pre-transgenic state. Two locus versions of ClvR, described herein provide a method for addressing these concerns, while also bringing about population alteration to a high frequency of transgene-bearing individuals under a variety of conditions of fitness cost and introduction frequency.

In some embodiments of the two vector system, the first vector comprises a DNA sequence modifying enzyme, wherein the DNA sequence modifying enzyme modifies an endogenous copy of an essential gene, and a promoter is operably linked to the DNA sequence modifying enzyme, and second vector comprising a rescue transgene sequence and a rescue transgene promoter operably linked to the rescue transgene sequence. In some embodiments, the two vectors are positioned on a single chromosome at a distance from each other. In some embodiments, the two vectors are positioned on a single extrachromosomal element at a distance from each other. In some embodiments, the two vectors are positioned on two different chromosomes. In some embodiments, the first vector is positioned on a chromosome and the second vector is positioned on an extrachromosomal element. In some embodiments, the second vector is positioned on a chromosome and the first vector is positioned on an extrachromosomal element. In some embodiments, the second vector optionally comprises one or more cargo sequences.

In some embodiments of the two-vector system, the first vector comprises a first sequence encoding a first component of a DNA sequence modifying complex, and a second sequence encoding the second component of the DNA sequence modifying complex wherein the DNA sequence modifying complex modifies an endogenous copy of an essential gene, and a first promoter that is operably linked to the first sequence encoding the first component and a second promoter is operably linked to the second sequence encoding the second component of the DNA sequence modifying complex, and a second vector comprising a rescue transgene sequence and a rescue transgene promoter operably linked to the rescue transgene sequence. In some embodiments, the two vectors are positioned on a single chromosome at a distance from each other. In some embodiments, the two vectors are positioned on a single extrachromosomal element at a distance from each other. In some embodiments, the two vectors are positioned on two different chromosomes. In some embodiments, the first vector is positioned on a chromosome and the second vector is positioned on an extrachromosomal element. In some embodiments, the second vector is positioned on a chromosome and the first vector is positioned on an extrachromosomal element. In some embodiments, the second vector optionally comprises one or more cargo sequences.

In some embodiments of the two-vector system, the first vector comprises a first sequence encoding a first component of a DNA sequence modifying complex, wherein the DNA sequence modifying complex modifies an endogenous copy of an essential gene, and a first promoter that is operably linked to the first sequence encoding the first component of the DNA sequence modifying complex, a rescue transgene, and rescue transgene promoter operably linked to the rescue transgene, and optionally one or more cargo transgenes, and a second vector comprising a second sequence encoding a second component of the DNA sequence modifying complex, and a second promoter operably linked to the second component of the DNA sequence modifying complex. In some embodiments, the two vectors are positioned on a single chromosome at a distance from each other. In some embodiments, the two vectors are positioned on a single extrachromosomal element at a distance from each other. In some embodiments, the two vectors are positioned on two different chromosomes. In some embodiments, the first vector is positioned on a chromosome and the second vector is positioned on an extrachromosomal element. In some embodiments, the second vector is positioned on a chromosome and the first vector is positioned on an extrachromosomal element. In some embodiments, the first vector optionally comprises one or more cargo sequences.

In some embodiments, a two-vector system is provided that comprises a first vector. The first vector comprises a first sequence encoding a first component of a DNA sequence modifying complex. The first vector also comprises a second sequence encoding a second component of the DNA sequence modifying complex. There is also a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex. There is also a second promoter operably linked to the second sequence encoding the second component of the DNA sequence modifying complex, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene. The two-vector system also comprises a second vector that comprises a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.

In some embodiments, a two-vector system is provided that comprises a first vector comprising: a first sequence encoding a first component of a DNA sequence modifying complex, a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences. The two-vector system also comprises a second vector that comprises a second sequence encoding a second component of the DNA sequence modifying complex; a second promoter operably linked to the second component of the DNA sequence modifying complex, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene.

In some embodiments, a two-vector system comprises a first vector that comprises a DNA sequence modifying enzyme; and a first promoter operably linked to the DNA sequence modifying enzyme, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene. The two-vector system also comprises a second vector that comprises a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.

In some embodiments, the “distance” is defined in terms of probability of recombination between the two vectors during each replication cycle. Without being limited by any particular theory, a 50% probability of recombination is equivalent to 50 map units or greater i.e., being equivalent to independent segregation. In some embodiments, the distance ranges from about 50 map units to about 100 map units. In some embodiments, the distance is about 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 map units, or a value within a range defined by any two of the aforementioned values. In some embodiments the distance is less than 50 map units. In some embodiments the distance ranges from about 0 map unit to about 50 map units. In some embodiments, the distance is about 0, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 map units, or a value within a range defined by any two of the aforementioned values.

In some embodiments, the DNA sequence modifying enzyme is encoded by a single gene, and the Cargo/Rescue transgenes can also be located at some distance from this gene on the same chromosome, or on different chromosomes. In some embodiments, the DNA sequence modifying enzyme is encoded by two tightly linked genes, and the Cargo/Rescue transgenes can also be located at some distance from these genes either on the same chromosome, or on different chromosomes (FIGS. 20A-D, FIGS. 21A-C). In some embodiments a first component of a DNA sequence modifying complex, and the Cargo/Rescue transgenes can also be located together, but at some distance from a second gene encoding a second component of the DNA sequence modifying enzyme on the same chromosome, or on different chromosomes (FIGS. 20B-D, FIGS. 21A-C). These embodiments create gene drive elements known as two locus ClvR. These are distinguished from those discussed above in which all components are tightly linked at a single locus (FIG. 20A). Behavior of single locus ClvR for several introduction frequencies and fitness costs is illustrated in FIG. 36. This figure also illustrates the effects of introducing wildtype individuals at timepoints after ClvR has spread to genotype fixation, such that wildtypes constitute 30% of the population following each introduction. The population rapidly rebounds to a state in which all individuals are Rescue- and thus cargo-bearing. These results are important because they illustrate that for many conditions single locus ClvR-dependent population replacement is not easily reversed through dilution of the population with wildtpes. In the case of two locus ClvR (e.g., involving a two-vector system), ClvR components are on two different chromosomes, and segregate independently at meiosis (FIGS. 20B-D), or they are located on the same chromosome at some distance from each other, such that recombination separates them at some frequency less than 50% of the time (FIGS. 21A-C and FIG. 50). This results in some gametes carrying the Cargo/Rescue but not Cas9/gRNA, others carrying Cas9/gRNA alone, and others carrying both transgene cassettes. The fate of these gametes in progeny (dead or alive) depends on when sequence modification occurs (in the germline alone or in somatic cells as well), and the presence or absence of the Cargo/Rescue. In short, the fates of the Cargo/Rescue and Cas9/gRNA components are dissociated because they do not always travel together through meiosis.

Without being limited by any particular theory, an implication of this behavior is that while with each two locus scenario the frequency of the Cargo/Rescue can increase in the population as compared to the non Cargo/Rescue bearing homologous chromosome (notwithstanding any limitations imposed by fitness costs associated with carrying the Cargo/Rescue cassette), the frequency of Cas9/gRNA (two locus version 1) (FIG. 20B or the Cas9/gRNA component not linked to the Cargo/Rescue (two locus version 2 and 3) (FIGS. 20C, D) will decrease over time since they sometimes find themselves in individuals who carry no functional copies of the essential gene, and are therefore dead (FIGS. 34A-F, FIGS. 35A-F and FIG. 50. Also see example 40 and 41, and associated figures, FIG. 49A-E and FIG. 50.). Since it is the presence of both Cas9 and gRNAs that leads to selection (indirectly, through the creation of LOF alleles of the essential gene) for the presence of the Cargo/Rescue, this means that in two locus ClvR the strength of drive (the ability create LOF alleles which select for Cargo/Rescue-bearing chromosomes and against their wildtype counterparts) wanes over time. Thus, two locus ClvR results in drive that is ultimately self-limiting, rather than self-sustaining, as is the case with single locus ClvR. Importantly, all the components of two locus ClvR already exist. They are exactly the same components as those used to implement ClvR^(tko) (FIGS. 29A-D, FIG. 30, FIGS. 42A-C) and ClvRs targeting other essential genes (dbe FIG. 26, FIG. 30) and (tf2As FIG. 27, FIG. 30). It is just that the components have been rearranged in terms of their chromosomal location. The behavior of two locus ClvR, version 1, is illustrated in FIGS. 34A-F. ClvR is introduced into the wildtype population at a fixed frequency of 40%, for illustrative purposes. Cas9/gRNAs cut in the male and female germline, and in embryos that derive from Cas9/gRNA-bearing mothers, due to maternal carryover of Cas9/gRNA. (left panel) Cargo/Rescue spreads to genotype fixation for a number of different fitness costs (up to and including 30%), but fails to spread when costs are higher (40-60%). Upper panels show the consequences of making a single introduction of wildtypes into the replaced/altered population at generation 200, such that wildtypes now make up 30% of the population. Lower panels show the consequences of five such introductions, one each 50 generations. More frequent introductions would result in more dramatic effects, since 50 generations provides an opportunity for some genotypes to rebound towards pre-introduction frequencies. Here, the 50 generation scenario is used to provide a conservative estimate picture of reversibility. Note that 30% introduction of wildtypes at generation 200 results in loss of Rescue from the population for all fitness costs except the zero fitness cost scenario, which is unlikely to exist in the wild. (middle panel) Frequency of Cas9/gRNAs over time. Note that the frequency decreases rapidly under all conditions when there is a fitness cost to carrying Cas9. In the case of no fitness cost (horizontal line with a square wave drop at generation 200) the frequency does not decrease because the Cargo/Rescue has gone to allele fixation and therefore there are no individuals lacking Rescue activity. This condition is unlikely to obtain in the real world. Introduction of wildtypes results in a decrease in the frequency of the cas9/gRNA under all conditions. In the case Cas9 does not result in a fitness cost to carriers, Cas9 is not eliminated. It simply undergoes the square wave transition as their numbers are diluted following the introduction of wildtypes. (right panel) Frequency of cleaved, LOF alleles of the essential gene for the conditions described in the left panel. Note that whenever ClvR spreads the frequency of the cleaved LOF allele goes to fixation. This occurs because the continuous presence of Cas9/gRNA ensures complete cleavage. Addition of wildtypes at a frequency of 30% results in loss of the cleaved allele over time when there is a fitness cost. This is because there is no further cleavage (Cas9/gRNAs have already been eliminated), and therefore no creation of new LOF alleles. In addition, because there is no drive, and therefore no selection for the presence of the Rescue, which also often carries a fitness cost, the Rescue is also lost from the population. Finally, with decreasing levels of Rescue, wildtype alleles of the essential gene are more fit than LOF alleles (because they allow survival in the absence of the Rescue), and therefore spread. In sum, while drive with two locus ClvR version 1 is strong (able to spread rapidly to high frequency while carrying a fitness cost), it is also transient, and therefore reversible through dilution with wildtypes (FIGS. 34A-F).

Similar qualitative points apply to the case of two locus ClvR, versions 2 and 3, which behave in an identical manner to each other with the given parameters (FIGS. 35A-F). These are illustrated in FIGS. 35A-F, FIGS. 49A-49E, and discussed in Example 40. They provide an example of an implementation of two-locus ClvR. Conditions are as in FIGS. 34A-F, with the exception that Cas9 and gRNA are split, with one linked to the Rescue/Cargo and the other located on a distinct chromosome. The behavior of these elements is qualitatively similar to that of two locus ClvR (version 1) (FIGS. 34A-F). In addition, versions 2/3 are particularly easy to create since they can be created simply by crossing two simple strains to each other: one strain carries germline-expressed Cas9; the other carries gRNA/Cargo/Rescue. Both are homozygous viable and populations heterozygous for two locus Clvr (version2/3) are created when the strains are crossed to each other. Note that for all two locus versions of ClvR this modeling assumes that maternally deposited Cas9 decays rapidly and therefore does not interact with zygotically expressed gRNAs in the early embryo. Other assumptions of the model are 90% cleavage, and 90% maternal carryover. In addition, fitness costs are additive and distributed across the components. Thus, for a 30% total homozygous fitness cost (homozygous at both loci) there is a 7.5 fitness cost for each allele of the Cargo/Rescue/Cas9 or gRNA, and the Cas9/gRNA component present on the other chromosome. Changing these variables does not qualitatively alter the outcome. All versions of two locus ClvR drive population replacement for some time, but then drive fades as components of the Cas9/gRNA decrease in frequency. In consequence of this decrease, population replacement becomes reversible through dilution with wildtypes.

In some embodiments, the two-vector versions of Clvr, using the components described herein, and the arrangements of components described herein, can also be implemented in formats in which ClvR components are located on the same chromosome, at some distance less than 50 map units from each other. In single locus ClvR the components are tightly linked, with very little or no recombination occurring between Cargo/Rescue and Cas9/gRNA. This makes drive strong and constant, since cleavage activity is always linked to the Cargo/Rescue. In the two locus versions of ClvR described above, Cargo/Rescue and Cas9/gRNA recombine freely with each other since they are on separate chromosomes. This is equivalent to a map distance of 50 map units or greater for two loci on the same chromosome (effectively unlinked). In considering these two extremes it is important to note that versions of two locus ClvR can also be created using the same procedures, with Cargo/Rescue and Cas9 components (either together or being separated such that one is linked to the Cargo/Rescue and one is not) being located on the same chromosome at something less than 50 map units distance. In this scenario, when individuals carrying both constructs on the same chromosome are released into a population, drive will initially be strong, reflecting linkage between the two sets of components (they travel together on the same chromosome more often than not). However, as recombination between the components occurs over subsequent generations, the loci will separate, with the rate of separation being dependent on the distance between the loci. Ultimately, recombination will create a situation identical to that observed with unlinked two locus ClvR, in which the two loci are in what is referred to as linkage equilibrium. The important point is that the smaller the recombination distance is between the two transgene cassette-bearing loci is, the longer the components will remain linked. In consequence, the strength of drive will decay more slowly than with unlinked two locus ClvR. It will start as strong as that of single locus Clvr. Recombination will slowly (depending on the distance between the loci) break up this association, resulting in drive with the self-limiting characteristics of unlinked two locus ClvR. Examples of ClvR with varying degrees of linkage are shown in Example 41, FIG. 50.

Without being limited by any particular theory, versions of two locus ClvR with linkage (FIGS. 21A-C and FIG. 50) are unique because they provide a method for titrating the strength of what is ultimately a self-limiting drive simply by changing the location of the two components on the same chromosome, with the strength and duration of drive being direct function of the degree of linkage: two locus ClvR with closely linked loci will have stronger drive (be able to spread more quickly and in the face of greater fitness costs), and drive for more generations, than will happen for two locus ClvRs with linkage in which the key genes are located farther apart. However, drive will ultimately be limited, as recombination occurs and the alleles approach linkage equilibrium.

In some embodiments, a two-vector system comprises a first vector comprising a DNA sequence modifying enzyme; a first promoter operably linked to the DNA sequence modifying enzyme, wherein the DNA modifying enzyme modifies an endogenous copy of an essential gene; and a second vector comprising a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences. Without being limited by any particular theory, the situation applies when the DNA sequence modifying complex is a base editor or an enzyme that does not require, for example, a guide RNA to modify an endogenous copy of an essential gene.

In some embodiments, a two-vector system comprises a first vector comprising a first sequence encoding a first component of a DNA sequence modifying complex; a second sequence encoding a second component of the DNA sequence modifying complex; a first promoter operably linked to the first sequence encoding the first component and a second sequence encoding the second component of the DNA sequence modifying complex, a second promoter operably linked to the second sequence encoding the second component, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene; and a second vector comprising a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.

In some embodiments, a two-vector system comprises a first vector comprising a first sequence encoding a first component of a DNA sequence modifying complex, a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex, a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences; and a second vector comprising a second sequence encoding a second component of the DNA sequence modifying complex; a second promoter operably linked to the second component of the DNA sequence modifying complex, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene. In some embodiments of the two-vector system, the first vector comprises the second sequence encoding the second component of the DNA sequence modifying complex, and the second vector comprises the first sequence encoding the first component of a DNA sequence modifying complex.

In some embodiments, the gene drive disclosed herein is an alternative form of gene drive that utilizes Cas9 or other nucleases to bring about cleavage and repair of an essential gene that does not involve or require homing, though homing can potentially contribute to drive (FIG. 25). This form of gene drive can also make use of base editing enzymes such as adenosine or cytosine deaminase to modify specific bases to create non-functional versions of an essential gene. It can also use Search and Replace Prime editing, which uses a Cas9 nickase linked to a reverse transcriptase, and a modified gRNA to introduce base changes or insertions or deletions. Without being limited by any particular theory, the mechanism simply involves a DNA sequence modifying enzyme such as Cas9, a set of gRNAs targeting an essential gene for cleavage, base editing, or Search and Replace Prime editing and a recoded version of the target essential gene that is immune to modification, linked as a single construct (by linked it is meant that they are not separated from each other during meiotic or other forms of recombination). This gene drive method is known as single locus ClvR (FIG. 20A). In some embodiments, individuals carrying one or more copies of this construct bring about modification of the sequence of one or more copies of the endogenous version of the essential gene such that it is no longer functional. Individuals who end up inheriting only non-functional versions of the essential gene die or are sterile, while those that carry one or more copies of the construct, which includes a rescue transgene, will survive and/or be fertile. Over multiple generations this behavior is predicted to result in the spread of the construct/vector into the population at the expense of the wild types version of the same chromosome (FIG. 1-5; FIGS. 31A-D; FIG. 36).

In some embodiments the gene drive disclosed herein is an alternative form of gene drive that utilizes Cas9 or other nucleases to bring about cleavage and repair of an essential gene that does not involve or require homing, though homing can potentially contribute to drive (FIG. 25). This form of gene drive can also make use of base editing enzymes such as adenosine or cytosine deaminase to modify specific bases to create non-functional versions of an essential gene. It can also use Search and Replace Prime editing, which uses a Cas9 nickase linked to a reverse transcriptase, and one or more modified gRNAs to introduce base changes or insertions or deletions. Without being limited by any particular theory, the mechanism involves the DNA sequence modifying enzyme such as Cas9 and a set of gRNAs targeting an essential gene for cleavage, (or a sequence targeted base editor) located at one position in the genome, with a recoded version of the target essential gene that is immune to modification, along with any associated cargo transgenes, located at another position in the genome. This gene drive method is known as two locus ClvR, version 1 (FIG. 20B). In some embodiments, individuals carrying one or both of these vectors bring about modification of the sequence of one or more copies of the endogenous version of the essential gene such that it is no longer functional. Individuals who end up inheriting only non-functional versions of the essential gene die or are sterile, while those that carry one or more copies of the rescue transgene and cargo, will survive and/or be fertile. Over multiple generations this behavior is predicted to result in the spread of the construct/vector into the population at the expense of the wild types version of the same chromosome. However, drive is ultimately limited in time (generations), and thus space (drive over generations in the presence of migration), and therefore allows for the possibility of reversal through dilution with wild types (FIGS. 34A-F).

In some embodiments the gene drive disclosed herein is an alternative form of gene drive that utilizes Cas9 or other nucleases to bring about cleavage and repair of an essential gene that does not involve or require homing, though homing can potentially contribute to drive (FIG. 25). This form of gene drive can also make use of base editing enzymes such as adenosine or cytosine deaminase to modify specific bases to create non-functional versions of an essential gene. It can also use Search and Replace Prime editing, which uses a Cas9 nickase linked to a reverse transcriptase, and a modified gRNA to introduce base changes or insertions or deletions. Without being limited by any particular theory, the mechanism involves a first component of the DNA sequence modifying enzyme such as Cas9 and a set of gRNAs targeting an essential gene for cleavage, (or a sequence targeted base editor) located at one position in the genome, with a recoded version of the target essential gene that is immune to modification, along with any associated cargo transgenes, and a second component of the DNA sequence modifying enzyme, located at another position in the genome. This gene drive method is known as two locus ClvR, version 2 and version 3 (FIGS. 20C,D). In some embodiments, individuals carrying one or both of these vectors bring about modification of the sequence of one or more copies of the endogenous version of the essential gene such that it is no longer functional. Individuals who end up inheriting only non-functional versions of the essential gene die or are sterile, while those that carry one or more copies of the rescue transgene and cargo, will survive and/or be fertile. Over multiple generations this behavior is predicted to result in the spread of the construct/vector into the population at the expense of the wild types version of the same chromosome. However, drive is ultimately limited in time (generations), and thus space (drive over generations in the presence of migration), and therefore allows for the possibility of reversal through dilution with wild types (FIGS. 35A-F).

In some embodiments, characterized and disclosed herein are multiple forms of this DNA sequence modification mediated drive. A discrete generation, deterministic population frequency model is used to demonstrate that there are a variety of conditions, that include various fitness costs, DNA sequence modification frequencies, and introduction frequencies, under which population replacement is predicted to occur.

Definitions

As used herein, the section headings are for organizational purposes only and are not to be construed as limiting the described subject matter in any way. All literature and similar materials cited in this application, including but not limited to, patents, patent applications, articles, books, treatises, and internet web pages are expressly incorporated by reference in their entirety for any purpose. When definitions of terms in incorporated references appear to differ from the definitions provided in the present teachings, the definition provided in the present teachings shall control. It will be appreciated that there is an implied “about” prior to the temperatures, concentrations, times, etc discussed in the present teachings, such that slight and insubstantial deviations are within the scope of the present teachings herein.

In this application, the use of the singular includes the plural unless specifically stated otherwise. Also, the use of “comprise”, “comprises”, “comprising”, “contain”, “contains”, “containing”, “include”, “includes”, and “including” are not intended to be limiting. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive. Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. See, for example Singleton et al., Dictionary of Microbiology and Molecular Biology 2nd ed., J. Wiley & Sons (New York, N.Y. 1994); Sambrook et al., Molecular Cloning, A Laboratory Manual, Cold Springs Harbor Press (Cold Springs Harbor, N.Y. 1989). For purposes of the present invention, the following terms are defined below. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. In this application, the use of the singular includes the plural unless specifically stated otherwise. In this application, the use of “or” means “and/or” unless stated otherwise. Furthermore, the use of the term “including”, as well as other forms, such as “includes” and “included”, is not limiting.

As used in this specification and claims, the singular forms “a,” “an” and “the” include plural references unless the content clearly dictates otherwise.

As used herein, “about” means a quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length that varies by as much as 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1% to a reference quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length.

As used herein, “regulatory element” refers to nucleic acid elements that can influence the expression of a coding sequence (for example, a gene) in a particular host organism. These terms are used broadly and encompass all elements that promote or regulate transcription, including promoters, core elements required for basic interaction of RNA polymerase and transcription factors, upstream elements, enhancers, and response elements (see, for example, Lewin, “Genes V” (Oxford University Press, Oxford) pages 847-873).

As used herein, the term “insertion site” refers a nucleic acid sequence that allows for insertion of the constructs as provided herein into a genome of a multicellular organism (for example, an insect genome). In some embodiments, a construct as provided herein can comprise a “insertion sequence” that allows for insertion of the construct into a genome of the host organism. Some embodiments that can be employed include the piggybac transposable element, mariner type transposable elements, and the P-element. Also, plasmids can be site specifically integrated into the genome using attb/attp or even by using CRISPR/Cas9, TALEN, MegaTAL and homologous recombination.

As used herein, a “vector,” interchangeably referred to as a transgenic construct, a targeting construct, or simply a construct, is a nucleic acid. As used herein, “nucleic acid” refers to deoxyribonucleic acid (DNA). In some embodiments, nucleic acid may refer to ribonucleic acid (RNA). In some embodiments, the construct as provided herein comprise one or more regulatory elements. Exemplary regulatory elements in prokaryotes include promoters, operators and ribosome binding sites. Regulatory elements that are used in eukaryotic cells can include, without limitation, transcriptional and translational control sequences, such as promoters, terminators, enhancers, insulators, splicing signals, polyadenylation signals, terminators, protein degradation signals, internal ribosome-entry element (IRES), 2A sequences, and the like, that provide for and/or regulate expression of a coding sequence and/or production of an encoded polypeptide in a host cell. For example, a promoter is a nucleotide sequence that permits binding of RNA polymerase and directs the transcription of a gene. Typically, a promoter is located in the 5′ non-coding region of a gene, proximal to the transcriptional start site of the gene. Sequence elements within promoters that function in the initiation of transcription are often characterized by consensus nucleotide sequences. Examples of promoters include, but are not limited to, promoters from bacteria, yeast, plants, viruses, and mammals (including humans). A promoter can be inducible, repressible, and/or constitutive. Inducible promoters initiate increased levels of transcription from DNA under their control in response to some change in culture conditions (for example, a change in temperature).

As used herein, “homologous recombination” refers to exchange of nucleotide sequences between two identical nucleic acid sequences. Homologous recombination also refers to exchange of nucleotide sequences between two similar nucleic acid sequences. In some embodiments, when the two nucleic acid sequences are similar, a similarity between the two nucleic acid sequences can be about 90% to about 99.9%. In some embodiments, the similarity between the two nucleic acid sequences can be about 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8 or 99.9%.

As used herein, “gene drive” refers to a situation in which genetic elements—including alleles of specific genes, gene complexes, entire chromosomes or endosymbiotic bacteria—are transmitted to viable, fertile progeny at rates greater than those due to Mendelian transmission, resulting in an increase in their frequency in the population over time, even if their presence results in a fitness cost to carriers. Without being limited by any particular theory, gene drive can occur by a number of mechanisms. In some embodiments gene drive has evolved in wild populations of various organisms, through a variety of mechanisms that are still under study (Burt and Trivers, 2006). In some embodiments, the gene drive is engineered. In some embodiments, the gene drive represents a naturally occurring mechanism or is engineered depending on the context and environment in which it occurs. A number of novel methods of engineering gene drive have also been proposed, and in several cases implemented.

In some embodiments, the present disclosure is related to vectors and methods for DNA sequence modification-based modification of populations, and beneficial and commercial applications of the vectors and methods.

In one implementation of this system, detailed below in the examples and sometimes referred to as CleaveR (also referred to herein as ClvR), the nuclease includes a member of the RNA-guided nucleases, such as Cas9. In this implementation Cas9 is expressed in the germline of male, females, or both sexes. Multiple gRNAs are also expressed, preferably three or four of them. They are designed to engage in Watson-Crick base pairing with, and therefore target for cleavage, distinct sequences within a target gene, so as to bring about its cleavage at multiple sites. These multiple breakages are expected to result in the creation of repair products—deletions, base changes, small additions—that create a non-functional version of the targeted gene. In summary, the purpose of the nuclease is to bring about loss-of-function (LOF) mutants of the targeted gene. As detailed in FIG. 25, DNA breaks in the target sequence can also be used to create LOF mutations in the target sequence when a cleavage-resistant LOF allele is used as a template for repair. There are two important characteristics of the system described thus far. First, the cassette encoding the nuclease can sit at any position in the genome. Second, the gene being targeted for inactivation is in some sense an essential gene: required for organism survival or fertility, broadly defined as fitness.

The second component of the CleaveR gene drive system is the existence of a version of the targeted essential gene that can rescue the lethality or infertility of those individuals in which both copies (for a diploid) of the essential gene have been inactivated, but that is itself resistant to cleavage by the RNA-guided Cas9 component of the construct. Resistance to cleavage is brought about by recoding the transgene so that it no longer productively interacts with the guide RNA Cas9 complex, according to rules that are well known in the field. Further recoding of the rescue transgene, in both the coding region and non-coding and regulatory regions, is also carried out. This recoding is done so as to minimize homology between the wildtype, endogenous version of the gene and the rescue version of the gene. This recoding is also done so as to minimize/eliminate the possibility that the cleaved version of the wildtype endogenous essential gene can be repaired and restored to functionality through ectopic homologous recombination, using the rescue transgene as a template for repair based on existing homology at the broken ends of the former. The literature provides guidance on the level of homology needed to prevent or promote homologous recombination. Without being limited by any particular theory, recoding can successfully achieved even when the rescue transgene has essentially no nucleotide homology to the endogenous copy of the gene. Demonstration that this can be achieved comes from multiple reports showing that bacterial and/or human versions of a large number of essential genes can successfully replace their yeast counterparts, resulting in yeast with high fitness.

Single Locus

In the single locus CleaveR construct, also often referred to as the vector or the construct, when these two genes are located near each other (tightly linked), they behave, as illustrated below, as a novel selfish genetic element, able to spread itself into a population and/or maintain itself in a population (bring about population replacement) under a variety of conditions that include varying levels of fitness cost associated with carrying the vector and any associated cargo genes, and introduction frequencies (FIG. 1-5; FIGS. 31A-D; FIG. 36). The details of these characters are described in more detail below.

Overview of CleaveR-Based Gene Drive

Without being limited by any particular theory, when the CleaveR construct is present in an organism, wildtype copies of the essential are at risk for cleavage and inactivation. The individuals carrying CleaveR themselves do not experience any cost from this cleavage, which happens in the germline and also in some cases in somatic cells, because they also carry a tightly linked copy of the rescue transgene. However, the gametes they pass on will in many cases not carry a functional copy of the endogenous essential gene, and they may also lack the CleaveR construct. In some cases the Cas9/gRNA complexes will also be deposited into oocytes/eggs, resulting in cleavage of the endogenous copy of the essential gene in early embryos that do not carry the CleaveR construct. In all of these cases, which arise through normal Mendelian segregation of chromosomes during meiosis in males and females, and in some cases diffusion or transport of Cas9/gRNA into daughter cells or products of cell-cell fusion (fertilization), progeny are often created that carry no functional copies of the essential gene. These individuals are of low fitness (dead, sterile or otherwise dysfunctional [flightless]) and do not contribute further to the population. Similar considerations apply with versions of two locus ClvR: whenever Cas9/gRNAs or other site-specific nucleases are present, they have the opportunity to cleave endogenous versions of the essential gene, creating LOF alleles.

The above behavior results in some loss in each generation of chromosomes and individuals that do not carry the CleaveR. This results, over multiple generations, in a progressive increase in the frequency of CleaveR-bearing individuals. Modeling, discussed further below, shows that under a variety of conditions CleaveR is predicted to spread to high frequency such that most or all individuals in the population bear at least one copy of the CleaveR chromosome (FIG. 1-5; FIGS. 31A-D; FIG. 36). The CleaveR chromosome is in some sense “held” in the population because as it has been spread (and the mechanism by which it has been spreading), it has necessarily caused inactivation of most or all of the wildtype copies of the essential gene. Thus the population has become “locked” into a configuration in which it now depends on the presence of CleaveR in order to maintain viability or fertility. In the case of two locus ClvR similar considerations apply, with the exception that what is driven into the population is the Rescue transgene and any other tightly linked transgenes. In addition, with versions of two locus ClvR reversal to a pre-transgenic (or low frequency transgenic) state is possible through dilution of the population with wildtypes, once the frequency of Cas9 and gRNAs (or some other site-specific nuclease that brings about cleavage of the essential gene) needed to cleave endogenous copies of the essential gene drops to low frequency. It should be understood that by low frequency it is meant lower than the initial frequency, with the number of wild types needed to bring about reversal being dependent on the frequency of Cas9 and gRNAs remaining in the population.

A similar principle, cleavage associated with rescue of those who carry the CleaveR vector, allows CleaveR to act as a gamete killer (known as spore killers in yeast), and to be able to force its inheritance in conditions in which it is episomal (as in a plasmid). In both cases the presence of the CleaveR element selects for those who carry it, and against those who fail to inherit it. Similar considerations apply in contexts in which the DNA sequence modifying enzyme makes it way into neighboring cells, through direct contact-mediated mechanisms or through release by a donor cell and uptake by a recipient cell: Cells that acquire the DNA sequence modifying enzyme but not the Rescue transgene are at risk of death through the creation of LOF alleles of an essential gene (FIG. 26).

In some embodiments, the method of gene drive described herein is agnostic as to the mechanism by which sequence modification-dependent inactivation of the essential gene is brought about. It can involve cleavage and error-prone repair, as discussed above. It can also involve the use of base editing enzymes known from the literature. It can also utilize other DNA modifying enzymes such as sequence targeted transposases, recombinases, integrases, topoisomerases, or other enzymes that can be targeted to specific sequences in DNA to bring about sequence changes. It can also use Search and Replace Prime editing, which uses a Cas9 nickase linked to a reverse transcriptase, and a modified gRNA to introduce base changes or insertions or deletions. Finally, it can also utilize homologous recombination when the template for repair of a wildtype cleaved allele is a previously cleaved, altered to LOF, and now cleavage insensitive allele, as a template for repair (FIG. 25). Importantly, the exact nature of the sequence changes brought about is not critical since there are many ways of rendering nonfunctional any particular gene through sequence modification.

In some embodiments, a vector is provided. The vector comprises: a first sequence encoding a first component of a DNA sequence modifying complex; a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex; a second sequence encoding a second component of a DNA sequence modifying complex; a second promoter operably linked to the second sequence encoding complex; a rescue transgene; a promoter operably linked to the rescue transgene that requires binding by the DNA sequence modifying complex for transcription of the rescue transgene; and optionally one or more cargo sequences.

In some embodiments, a two-vector system is provided that comprises: a first vector. The first vector comprises: a first sequence encoding a first component of a DNA sequence modifying complex; a second sequence encoding a second component of the DNA sequence modifying complex; a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex, a second promoter operably linked to the second sequence encoding the second component of the DNA sequence modifying complex. The DNA modifying enzyme complex modifies an endogenous copy of an essential gene. The system comprises a second vector that comprises a rescue transgene sequence; a promoter operably linked to the rescue transgene that requires binding by the DNA sequence modifying complex for transcription of the rescue transgene; and optionally, one or more cargo sequences.

In some embodiments a two-vector system is provided that comprises a first vector that comprises a first sequence encoding a first component of a DNA sequence modifying complex, a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex, a rescue transgene sequence; a promoter operably linked to the rescue transgene that requires binding by the DNA sequence modifying complex for transcription of the rescue transgene; and optionally, one or more cargo sequences. The two-vector system further comprises a second vector that comprises a second sequence encoding a second component of the DNA sequence modifying complex; and a second promoter operably linked to the second component of the DNA sequence modifying complex. The DNA modifying enzyme complex modifies an endogenous copy of an essential gene. In some embodiments, the first vector comprises the second sequence encoding the second component of the DNA sequence modifying complex, and the second vector comprises the first sequence encoding the first component of a DNA sequence modifying complex.

Vectors

FIG. 15A-FIG. 15C, FIG. 38A-FIG. 38C, FIG. 42A show embodiment of single locus ClvR construct design and principle according to the present disclosure (Example 15, Example 17). In some embodiments, the disclosure is related to a vector. In some embodiments, the vector comprises a first gene encoding a DNA sequence modifying enzyme. In some embodiments, the DNA modifying enzyme modifies the sequence of an endogenous copy of an essential gene. As used herein, an “essential gene” is defined as a gene that is critical for survival, growth or fertility, and whose loss of function is either lethal, prevents growth or is sterilizing. Some essential genes are critical for survival under all circumstances. Some essential genes are critical for survival only under particular circumstances and/or particular environmental conditions (e.g., in the presence of toxic drugs, toxins, etc., or in the absence of nutrients, vitamins, etc.). In some embodiments, more than one or more endogenous copies of the essential gene are present. In some embodiments, when one or more endogenous copies of the essential gene are present they are alleles or allelic variants of the essential gene. As used herein, the “endogenous copy” refers to the wild type version of the essential gene.

In some embodiments, a vector comprises a first promoter operably linked to the first gene encoding the DNA sequence modifying enzyme. In some embodiments, the first gene is operably linked to one or more additional regulatory elements. In some embodiments, the vector further comprises a second gene encoding a rescue transgene. In some embodiments of the vector, a second promoter is operably linked to the rescue transgene. In some embodiments, the second gene is operably linked to one or more additional regulatory elements. In some embodiments a third and fourth gene (cargo genes/dominant markers), including promoters linked to these genes are also present (c.f. FIGS. 42A-C).

In some embodiments multiple vectors are created. FIGS. 20A-D-FIGS. 21A-C show embodiments of two locus ClvR construct design and principle according to the present disclosure (Examples 28-30).

In some embodiments, the vector or one of the vectors in the case of a two locus configuration optionally comprises one or more cargo sequences. In some embodiments, a cargo sequence is a nucleic acid. In some embodiments, the vector is configured to be positioned in a chromosome. In some embodiments, the vector is configured to be positioned in an extra-chromosomal element. Non-limiting examples of cargo genes include are sequences encoding antibodies against Plasmodium, the causal agent of malaria (Isaacs et. al. 2011, Hollingdale et. al. 1984, and Li et. al. 2005), or non-coding RNAs to bring about cleavage of the dengue virus RNA genome (Yen et. al. 2018, Franz et. al. 2006, Mathur et. al. 2010, Travanty et. al. 2004, and Castillo et. al. 2016). In some embodiments, the vector or vectors are configured to be positioned in a chromosome and an extra chromosomal element. In some embodiments, the vector or vectors are configured to be positioned in a chromosome but not in an extra chromosomal element. In some embodiments, the vector or vectors are configured to be positioned in an extra chromosomal element but not in a chromosome.

In some embodiments, the DNA sequence modifying enzyme is a nuclease. Non-limiting examples of nucleases include Flap endonucleases, restriction endonucleases (e.g., F-EcoT5I, F-EcoT5II, F-EcoT5IV, F-SceI, F-TevI, F-TevII, I-AchMI, I-AniI, I-BasI, I-BmoI, I-Bth0305I, I-BthII, I-BthORFAP, I-CeuI, I-ChuI, I-CpaI, I-CpaII, I-CreI, I-CsmI, I-CvuI, I-DdiI, I-DmoI, I-GpiI, I-GzeI, I-HjeMI, I-HmuI, I-HmuII, I-LlaI, I-LtrI, I-LtrWI, I-MpeMI, I-MsoI, I-NanI, I-NitI, I-NjaI, I-OnuI, I-PakI, I-PanMI, I-PnoMI, I-PogTE7I, I-PorI, I-PpoI, I-ScaI, I-SceI, I-SceII, I-SceIII, I-SceVI, I-SpomI, I-SscMI, I-Ssp6803I, I-TevI, I-TevII, I-TevIII, I-TslI, I-TslWLAY76, I-Vdi141I, PI-AvaI, PI-BciPI, PI-HvoWI, PI-MleSI, PI-Mtul, PI-PkoI, PI-PkoII, PI-PspI, PI-SceI, PI-TfuI, PI-TfuII, PI-TliI, PI-TliII, PI-TmaI, PI-TmaKI), Cas9, and Cas9-like enzymes (including but not limited to CPf1, C2c1, C2c2, and C2c3 (Shmakov et. al. 2015, Shmakov et. al. 2017, Koonin et. al. 2017-1, Koonin et. al. 2017-2), ZFNs, MegaTALs, TALENs, HEGs, meganucleases, and Search and Replace Prime editors, which use a Cas9 nickase linked to a reverse transcriptase, and a modified gRNA to introduce base changes or insertions or deletions.

In some embodiments, DNA modifications are achieved through cleavage by site-specific nucleases. Without being limited by any particular theory, it should be understood that equivalent effects can be obtained through the use of any enzyme that brings about modification of a target DNA sequence. Non-limiting examples include cytosine and adenine base changes brought about through the targeted use of deaminases and site-specific integrases. It can also use Search and Replace Prime editing, which uses a Cas9 nickase linked to a reverse transcriptase, and a modified gRNA to introduce base changes or insertions or deletions.

In some embodiments, the nuclease cleaves the endogenous copy of the essential gene. In some embodiments, the nuclease generates one or more double strand breaks in the endogenous copy of the essential gene. In some embodiments, the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene. In some embodiments, the one or more double strand breaks in the endogenous copy of the essential gene are staggered. In some embodiments, the one or more double strand breaks in the endogenous copy of the essential gene are not staggered. In some embodiments, the nuclease cleaves and generates one or more single strand breaks in the endogenous copy of the essential gene.

In some embodiments, the one or more double strand breaks (DSBs) are repaired. In some embodiments, the one or more DSBs are repaired to create an altered sequence of the essential gene. In some embodiments, the one or more DSBs are repaired by one or more of non-homologous end joining (NHEJ), microhomology-mediated end joining (MMEJ), homologous recombination (HR), complete HR, and incomplete HR. nicking, followed by reverse transcription and ligation, and incomplete HR In some embodiments, the altered sequence comprises substitutions, insertions, deletions, frame-shifts, or a combination thereof.

In some embodiments, the DNA sequence modifying enzyme is a base editor. Non-limiting examples of a base editor include cytosine deaminase, and adenine deaminases.

In some embodiments, the base editor creates one or more base changes in endogenous copy of the essential gene. In some embodiments, the one or more base changes comprise transitions, transversions, or both. In some embodiments, the one or more base changes occur due to tautomerism, depurination, deamidation, or a combination thereof. In some embodiments, the one or more base changes create an altered sequence of the essential gene. In some embodiments, the one or more base changes comprise one or more point mutations in the endogenous copy of the essential gene. In some embodiments, the one or more point mutations comprise frameshift mutation, nonsense mutation, missense mutation, small deletions or additions, neutral mutation, silent mutation, or a combination thereof.

In some embodiments, the DNA sequence modifying enzyme is a Search and Replace Prime editor, which uses a Cas9 nickase linked to a reverse transcriptase, and a modified gRNA to introduce base changes or insertions or deletions.

In some embodiments, the Search and Replace Prime editor creates one or more base changes in endogenous copy of the essential gene. In some embodiments, the one or more base changes comprise transitions, transversions, or both. In some embodiments, the one or more base changes occur due to tautomerism, depurination, deamidation, or a combination thereof. In some embodiments, the one or more base changes create an altered sequence of the essential gene. In some embodiments, the one or more base changes comprise one or more point mutations in the endogenous copy of the essential gene. In some embodiments, the one or mutations comprise frameshift mutation, nonsense mutation, missense mutation, small deletions or additions, neutral mutation, silent mutation, or a combination thereof.

In some embodiments, the promoter of the first gene expresses within females such that the DNA-modifying enzyme produced by the first gene is deposited into eggs and can modify target sequences inherited from a father who lacks the vector. This activity, while unnecessary for the majority of cases wherein this drive method successfully replaces a population, results in more rapid population replacement than without, for a given fitness cost and/or introduction frequency. Where the DNA-modifying enzyme is a version of Cas9 or a Cas9-related enzyme (guided to a target sequence by a guide RNA), both Cas9 and any and all associated gRNAs are deposited into the eggs of such females together to enable modification of alleles inherited from a non-vector bearing male (Example 17, FIG. 42B).

In some embodiments, there is paternal carryover of the DNA modifying enzyme, allowing for modification of alleles inherited from the mother, even in those who have not inherited the vector.

In some embodiments, the rescue transgene is a recoded copy of the essential gene. In some embodiments, when the rescue transgene is a recoded copy of the essential gene, the protein encoded by the recoded copy of the essential gene (recoded protein) is about 90% to about 99.9% identical to protein encoded by the endogenous copy of the essential gene (endogenous protein). In some embodiments, the recoded protein is about 50, 52.5, 55, 57.5, 60, 62.5, 65, 67.5, 70, 72.5, 75, 77.5, 80, 82.5, 85, 87.5, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, or 99.9% to the endogenous protein. In some embodiments, the rescue transgene is a gene of unrelated sequence. In some embodiments, when the rescue transgene is a gene of unrelated sequence, the protein encoded by the recoded copy of the essential gene (recoded protein) is functionally equivalent to the protein encoded by the endogenous copy of the essential gene (endogenous protein). In some embodiments, the DNA sequence modifying enzyme does not modify the rescue transgene.

In some embodiments, the chromosome in which the vector or vectors are positioned is one or more of an autosome, X chromosome, Y chromosome, Z chromosome, W chromosome, or supernumerary chromosome. In some embodiments, the vector or vectors are positioned in one or more combinations of an autosome, X chromosome, Y chromosome, Z chromosome, W chromosome, or supernumerary chromosome. For example, in some embodiments, the vector or vectors are positioned in an autosome and an X chromosome, in some embodiments, the vector or vectors are positioned in an autosome and a Y chromosome, in some embodiments, the vector or vectors are positioned in an autosome and a supernumerary chromosome, in some embodiments, the vector or vectors are positioned in an X chromosome and a Y chromosome, in some embodiments, the vector or vectors are positioned in an X chromosome and a supernumerary chromosome, in some embodiments, the vector or vectors are positioned in an Y chromosome and a supernumerary chromosome, in some embodiments the vector or vectors are positioned on some combination of chromosomes that include either the Z chromosome or the W chromosome, and in some embodiments, the vector is positioned in an autosome, X chromosome, Y chromosome, and supernumerary chromosome.

In some embodiments, the vector or vectors are positioned in an extra-chromosomal element. In some embodiments, the extra-chromosomal element is a plasmid. In some embodiments, the extra-chromosomal element is a virus. In some embodiments, the extra-chromosomal element is a plasmid and a virus. In some embodiments, the vector or vectors are positioned in combinations of one or more chromosomes and one or more extra-chromosomal elements.

In some embodiments, the vector or vectors optionally comprises one or more cargo sequences. In some embodiments, the one or more cargo comprise foreign gene sequences, or one or more alleles of an endogenous chromosomal or extra-chromosomal gene.

In some embodiments the cargo comprises one or more alleles of an endogenous chromosomal or extra-chromosomal gene to which the vector or one of the vectors has been linked through nearby insertion on the chromosome or extra-chromosomal element that carries the endogenous allele of interest.

In some embodiments, the cargo can be physically part of the vector or one of the vectors prior to its insertion in a chromosomal or an extra-chromosomal element. In some embodiments, the cargo can be a chromosomal/extra-chromosomal allele of a gene that becomes linked to the vector or vectors after the insertion of the vector near that allele. In some embodiments, a fraction of the cargo can be physically part of the vector or one or more of multiple vectors prior to its insertion in a chromosomal or an extra-chromosomal element, and a remainder of the cargo can be a chromosomal/extra-chromosomal allele of a gene that becomes linked to the vector after the insertion of the vector near that allele. In some embodiments, the cargo does not have to be a part of the vector or vectors, i.e., in some embodiments, the cargo is optional and can be physically part of the vector prior to its insertion in a chromosomal or an extra chromosomal element. In some embodiments, the cargo does not have to be a part of the vector, i.e., in some embodiments, a fraction of the cargo can optionally be physically part of the vector prior to its insertion in a chromosomal or an extra chromosomal element, and a remainder of the cargo can be a chromosomal/extra-chromosomal allele of a gene that becomes linked to the vector after the insertion of the vector near that allele.

In some embodiments herein, the vector comprising the first gene encoding the DNA sequence modifying enzyme and the second gene encoding the rescue transgene is referred to as CleaveR (e.g., FIG. 6; FIG. 7; FIG. 10; FIG. 20A; FIG. 42A), which comprises and/or consists of two components: (1) a site-specific DNA modifying enzyme designed to alter the sequence of an endogenous gene required for survival, proliferation, fertility, or differentiation so as to render it non-functional; (2) a recoded version of the essential gene resistant to cleavage, and having reduced nucleotide identity with the endogenous gene. Optionally, one or more cargo sequences are present.

In some embodiments herein, two vectors are present (the components of which can be used for any of the single vector or single locus arrangements provided herein). The first comprises the first gene encoding the DNA sequence modifying enzyme or a first fragment of the DNA sequence modifying enzyme. The second gene encodes the rescue transgene, any cargo transgenes, and optionally a second fragment of the DNA sequence modifying enzyme. These variants are referred to as two locus CleaveR (e.g., FIGS. 20B-D; FIGS. 21A-C), which comprises and/or consists of two vectors that incorporate the following: (vector 1) a site-specific DNA modifying enzyme or first fragment thereof, designed to alter the sequence of an endogenous gene required for survival, proliferation, fertility, or differentiation so as to render it non-functional; (vector 2) a recoded version of the essential gene resistant to cleavage, and having reduced nucleotide identity with the endogenous gene (right). Optionally, one or more cargo sequences are present; optionally a second fragment of the DNA sequence modifying enzyme is present.

In some embodiments, DNA sequence modifying enzyme is, without limitation, Cas9, Cas-9-related RNA-guided nucleases, ZFNs, TALENs, homing endonucleases, restriction enzymes, natural site-specific nucleases, engineered site-specific nucleases, base editing enzymes, cytidine deaminase, and adenine deaminase.

In some embodiments, the vector or the vectors further comprises one or more additional sequences. In some embodiments, the one or more additional sequences allow the vector or vectors to be positioned in the chromosome. In some embodiments, the one or more additional sequences allow the vector or vectors to be positioned in the extra-chromosomal element. In some embodiments, the one or more additional sequences allow the vector or vectors to be positioned in the chromosome and the extra-chromosomal element. In some embodiments, the one or more additional sequences allow the vector or vectors to be positioned in the chromosome but not the extra-chromosomal element. In some embodiments, the one or more additional sequences allow the vector or vectors to be positioned in the extra-chromosomal element but not the chromosome.

In some embodiments, the one or more additional sequences is, without limitations, transposase binding site, LTRs, recombinase binding site, a sequence with homology to a desired location on the chromosome or a sequence with homology to a desired location on the extra-chromosomal element, or combinations thereof.

In some embodiments, the vector or vectors further comprises one or more additional sequences, wherein the one or more additional sequences serve as dominant marker genes that allow individuals carrying the vector to be easily identified either visually, as with expression of a fluorescent protein, or by virtue of surviving a negative selection procedure, as with expression of a gene that encodes resistance to a toxin (such as an antibiotic, insecticide, herbicide), in the presence of the toxin. In some embodiments, the vector or vector comprises one or more sequences that encode marker proteins that can be expressed under the control of suitable regulatory elements. Non-limiting examples of marker proteins include dsRed, GFP, EGFP, CFP, ECFP, BFP, EBFP, mHoneydew, mBanana, mOrange, tdTomato, mTangering, mStrawberry, mCherry, mGrape1, mGrape2, mRaspberry, mPlum, YFP or EYFP, and can be chosen by one of skilled in the art according to need. Fluorescent marker protein can be visualized by illuminating with a suitable excitatory wavelength and observing the fluorescence (e.g., by fluorescence microscopy). In some embodiments, a marker protein would allow for easy identification of organisms carrying the vector.

In some embodiments, the first promoter is, without limitations, a germline promoter, a male specific germline promoter, a female specific germline promoter, a cell-type specific promoter, a tissue-specific promoter, a ubiquitous promoter, a promoter activated at a specific stage of mitosis, a promoter activated at a specific stage of meiosis, or combinations thereof.

In some embodiments, the size of the one or more cargo sequences ranges from about is about 0.5 kb to about 500 kb. In some embodiments, the size ranges from about 1 kb to about 1000 kb. In some embodiments, the size ranges from about 5 kb to about 5000 kb. In some embodiments, the size ranges from about 10 kb to about 10000 kb. In some embodiments, the size is about 0.1, 0.5, 1, 5, 10, 25, 50, 75, 100, 250 500, 750 1000, 2500, 5000, 7500, or 10000 kb.

In some embodiments, the nuclease comprises at least one nuclease domain. In some embodiments, the nuclease comprises one or more DNA binding domains. In some embodiments, the nuclease comprises at least one nuclease domain and one or more DNA binding domains.

In some embodiments, when the nuclease is Cas9 or a Cas9-related enzyme, the vector further comprises one or more genes encoding one or more guide RNAs. In some embodiments, involving two locus ClvR, the two vectors will each comprise either Cas9 or gRNAs, such that cleavage only occurs when both are present. In some embodiments, the guide RNA enables the nuclease to target specific DNA sequences through Watson-Crick base pairing, thereby allowing targeting of very many positions in any genome. In some embodiments, the guide RNA enables the nuclease to target specific sequences within the endogenous copy of the essential gene. In some embodiments, the guide RNA enables the nuclease to target specific sequences within the protein coding region of endogenous copy of the essential gene. In some embodiments, the guide RNA allows the nuclease to target specific sequences within the non-coding region of endogenous copy of the essential gene. In some embodiments, the guide RNA allows the nuclease to target specific sequences outside the endogenous copy of the essential gene.

In some embodiments, when the nuclease is Cas9, the nuclease domain of Cas9 is deliberately inactivated through one or more mutations and the vector comprises a different nuclease domain. In some embodiments, the different nuclease domain is single chain variant of FokI. In some embodiments, when the DNA binding domain is a TALE, the nuclease domain is provided as a single active nuclease domain. In some embodiments, the single active nuclease domain is a single chain variants of FokI. In some embodiments of the vector, when the DNA binding domain is a TALE, the nuclease domain is provided as a single active nuclease domain, such as single chain variants of FokI (Sun and Zhao 2014).

In some embodiments of single locus and two locus ClvR the separation of a functional Rescue from the Cargo can be prevented by locating the Cargo in an intron of the Rescue (FIG. 22). A break between the two genes followed by reciprocal end joining with the same region on the homologous chromosome could separate them. Locating the ClvR cargo in an intron of the Rescue transgene (bottom panel) reduces breakage and end joining-mediated separation of a functional Rescue (the component driven into the population by ClvR) from the Cargo. Separation could otherwise generate empty ClvR elements (ClvR^(Δcargo), top panel), or Rescue only elements (ClvR^(rescue), middle panel), the spread of which provide no beneficial function. Crossed lines indicate sites of chromosome breakage and end joining with a similar position on a homologous chromosome. Recombinant products of interest are indicated by the dotted lines.

In some embodiments of single and two locus ClvR separation of a functional Rescue from the Cargo can be reduced by locating the Cargo between two transgenes whose co-expression is required to produce a functional Rescue essential enzyme, such as dihydrofolate reducatse (FIG. 23). The 5′ half of DHFR is driven by its own promoter. The 3′ half is driven by a strong ubiquitous promoter. The two domains are brought together to form an active enzyme through heterodimerization, mediated by specific domains at the N-terminus of each protein (boxes with diagonal lines).

In some embodiments of single and two locus ClvR separation of a functional Rescue from the Cargo can be reduced by locating the Cargo between two transgenes whose co-expression is required to produce a functional Rescue protein (FIG. 24). Here this is achieved using a two-component transcription-based system. The essential gene promoter drives the expression of a heterologous transcriptional activator such as GAL4. The Rescue transgene contains GAL4 UAS binding sites sufficient to drive GAL4-dependent expression, upstream of an otherwise promoterless, recoded Rescue transgene.

In some embodiments of single and two locus ClvR Cas9 can be made essential for Rescue function. A circuit that selects against mutation of Cas9/gRNAs to inactivity is illustrated in FIG. 32. In this implementation a variant of Cas9 known as Cas9-VPR includes a domain that can activate transcription following DNA binding. Cas9-VPR can also bring about cleavage of full length target sites. Importantly, however, Cas9-VPR can also bind truncated gRNA target sites and drive transcription of a nearby gene, without cleaving these sites. In this way the exact same gRNAs and Cas9 are used for cleavage and transcriptional activation. The figure illustrates an implementation in which Cas9 expression is driven by the promoter of the essential gene. The gRNAs are expressed ubiquitously under U6 promoter control, as usual. Cas9 and gRNAs will cleave the wildtype copy of the essential gene in all tissues in which the essential gene is expressed. Cas9 and gRNAs will also drive expression of a promoterless, recoded version of the essential gene (the Rescue) in these same tissues. The system thus creates tight linkage between components required for cleavage and those required for rescue. It can fail due to point mutations in Cas9 that allow target site DNA binding and transcriptional activation but that prevent cleavage, as with dead Cas9 variants used for transcriptional regulation or visualization of specific genomic loci. These will happen, but are very specific mutations, and thus any spread of dead Cas9 within the population should be delayed. An important requirement for this approach is that the essential gene be expressed in the germline at levels sufficient to bring about Cas9-dependent germline cleavage of the wildtype essential gene. Also note that unless the essential gene is only required in the germline, Cas9 will be expressed and active in some somatic tissues.

Methods

One of ordinary skill in the art would appreciate that any of the methods disclosed herein can be performed by any of the vectors provided herein.

In some embodiments, a method of modifying a population by a vector or vectors is provided. In some embodiments, the method comprises obtaining an organism of the population. In some embodiments, the organism is, without limitations, bacteria, archaea, fungi, plants and animals, including rodents, amphibians, mammals, reptiles, insects, mosquitoes, fish, etc.

In some embodiments, the method comprises positioning the vector or vectors in at least one chromosome or extra-chromosomal element in the organism. In some embodiments, the vector or vectors is any of the embodiments of the vectors provided herein.

In some embodiments, the DNA sequence modifying enzyme is expressed in the organism. In some embodiments, the organism is unicellular or multicellular. In some embodiments, when the organism is multicellular, the DNA sequence modifying enzyme is expressed in all cells of the organism. In some embodiments, the DNA sequence modifying enzyme is not expressed in all cells of the multicellular organism. In some embodiments, the DNA sequence modifying enzyme is expressed in a fraction of cells of the multicellular organism. In some embodiments, the DNA sequence modifying enzyme is expressed only in the male or female germline, or in the germline of both sexes.

In some embodiments, the expression of the DNA sequence modifying enzyme induces one or more sequence modifications. In some embodiments, the expression of the DNA sequence modifying enzyme induces one or more sequence modifications in an essential gene. In some embodiments, the expression of the DNA sequence modifying enzyme induces one or more sequence modifications in an essential gene in one or more cells in the organism. In some embodiments, the one or more sequence modifications result in the essential gene being rendered partially non-functional. In some embodiments, the one or more sequence modifications result in the essential gene being rendered wholly non-functional. In some embodiments, the one or more sequence modifications result in the essential gene being rendered partially non-functional in some circumstances and wholly non-functional in other circumstances. In some embodiments, the result of the essential gene being rendered partially or wholly non-functional is in a defect in the organism. In some embodiments, the defect is, without limitations, a defect in survival, growth control, fertility, differentiation, or combinations thereof.

In some embodiments, the defect occurs when the one or more cells in which the essential gene being rendered partially or wholly non-functional lack a rescue transgene. In some embodiments, the rescue transgene expresses a recoded protein that rescues the defects in survival, growth control, differentiation, or combinations thereof.

In some embodiments, the expression of the recoded protein by the rescue transgene results in the generations of an altered organism. In some embodiments, the altered organism expresses the recoded protein in the one or more cells in which the essential gene has been rendered partially non-functional. In some embodiments, the altered organism expresses the recoded protein in the one or more cells in which the essential gene has been rendered wholly non-functional. In some embodiments, the altered organism expresses the recoded protein in the one or more cells in which the essential gene has been rendered partially non-functional in some circumstances and wholly non-functional in other circumstances.

In some embodiments, the altered organism carries one or more copies of the vector or vectors, and wherein the defects in survival, growth control, or differentiation of the one or more cells in which the essential gene has been rendered partially non-functional have been rescued the rescue transgene expressed from the one or more copies of the vector or vectors. In some embodiments, the altered organism carries one or more copies of the vector or vectors, and wherein the defects in survival, growth control, or differentiation of the one or more cells in which the essential gene has been rendered wholly non-functional have been rescued the rescue transgene expressed from the one or more copies of the vector or vectors. In some embodiments, the altered organism carries one or more copies of the vector or vectors, and wherein the defects in survival, growth control, or differentiation of the one or more cells in which the essential gene has been rendered partially non-functional in some circumstances and wholly non-functional in other circumstances have been rescued the rescue transgene expressed from the one or more copies of the vector or vectors.

In some embodiments, the altered organism is introduced in a population. In some embodiments, the altered organism is introduced in a population in which an increase in a frequency of the altered organism is desired relative to a frequency of a wild type organism. In some embodiments, the altered organism is introduced in a population in a particular environment. In some embodiments, the altered organism is introduced in a population in a particular environment in which an increase in a frequency of the altered organism is desired relative to a frequency of a wild type organism in the population in the particular environment. In some embodiments, the altered organisms is introduced in the population such that the percent of the altered organism in the population ranges from about 0.0001% to about 50%. In some embodiments, the percent is about 0.00001, 0.0005, 0.0001, 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 20, 30, 40, or 50%. In some embodiments, the percent is greater than 100%, so as to achieve a more rapid change in the population.

In some embodiments, introducing the altered organism in the population results in replacement of the wild type organism with the altered organism in the population. In some embodiments, introducing the altered organism in the population results in replacement of the wild type organism with the altered organism in the population in the particular environment.

In some embodiments, the altered organism exhibits one or more altered traits. In some embodiments, the altered organism introduces and spreads one or more traits of interest in the population. In some embodiments, the one or more traits of interest is a novel trait not previously prevalent in the population, a trait that is a modified version of a trait previously present in the population (e.g., an enhance or a suppressed version of a trait previously present in the population) or a combination thereof. In some embodiments, the population is modified by the introduction of the altered organism in the population. In some embodiments, the population is modified by the introduction of the altered organism in the population in the particular environment. In Non-limiting examples of traits of interest to enhance or decrease include but are not limited to pathogen resistance, insecticide resistance, environmentally triggered death or sterility, herbicide resistance, fungicide resistance, phage resistance, resistance to viral infection, resistance to abiotic environmental factors, such as cold, heat, and stress.

In some embodiments, the population is modified by the introduction of the altered organism in the population. In some embodiments, the population is modified by the introduction of the altered organism in the population in the particular environment. Non-limiting examples of traits of interest include but are not limited to pathogen resistance, insecticide resistance, environmentally triggered death or sterility, herbicide resistance, fungicide resistance, phage resistance, resistance to viral infection, resistance to abiotic environmental factors, such as cold, heat, and stress. In some embodiments the population is modified such that gene drive is limited in time and space by segregation of the vectors that make up versions of two locus ClvR.

In some embodiments, the population is modified by the introduction of the altered organism in the population. In some embodiments, the population is modified by the introduction of the altered organism in the population in the particular environment. In non-limiting examples of traits of interest include but are not limited to pathogen resistance, insecticide resistance, environmentally triggered death or sterility, herbicide resistance, fungicide resistance, phage resistance, resistance to viral infection, resistance to abiotic environmental factors, such as cold, heat, and stress. In some embodiments the modified population is eliminated or greatly decreased with respect to one or more component transgenes through dilution of the population with wildtypes.

In some embodiments, a method of reversibly modifying a population is provided. In some embodiments, the method comprises obtaining a wild type organism, positioning a two-vector system in the wild type organism generating an altered organism by inducing one or more sequence modifications in an essential gene by a DNA sequence modifying enzyme/complex in the two-vector system that result in a defect in survival, growth control, fertility, or differentiation in one or more cells in the organism, and rescuing the defect in survival, growth control, fertility, or differentiation by a rescue transgene in the two-vector system, introducing the altered organism in an environment wherein an increase in a frequency of the altered organism is desired relative to a frequency of the wild type organism in a population; replacing the wild type organism with the altered organism in the population in the environment, thereby obtaining a modified population. In some embodiments one can then reintroduce the wild type organism in an environment wherein an increase in a frequency of the wild type organism is desired relative to a frequency of the modified organism in the modified population. This will result in replacing the modified organism with the wild type organism in the modified population in the environment, thereby reversibly modifying the population.

In some embodiments of the method, the one or more cells comprise somatic cells, germline cells, gametes, or a combination thereof.

In some embodiments of the method, the altered organism is heterozygous or homozygous for one or both of the vectors.

In some embodiments of the method, the organism is haploid, diploid, or polyploid.

In some embodiments of the method, the reversible modification of the population occurs at a rapid rate, high frequency, or both. In some embodiments of the method, the rapid rate is defined as replacement of at least 90% of the wild type organism by the altered organism or vice versa in the population after at most 100 generations. In some embodiments of the method, the high frequency is defined as replacement of at least 90% of the wild type organism by the altered organism or vice versa after 100 generations in the population.

In some embodiments, an organism with the defect in survival, growth control, fertility, or differentiation of the one or more cells is eliminated if the one or more cells of the organism lack the rescue transgene.

In some embodiments, the DNA sequence modifying enzyme does not modify the rescue transgene.

In some embodiments, rescuing the defects in one or more of survival, growth control, or differentiation is achieved by restoring one or more of normal survival, growth control, fertility, or differentiation of the one or more cells by the rescue transgene.

In some embodiments, the one or more cells comprise somatic cells, germline cells, gametes, or a combination thereof.

In some embodiments, the DNA sequence modifying enzyme is a nuclease, a base editor, or a Search and Replace Prime editor according to the embodiments herein.

In some embodiments, the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene as described herein.

In some embodiments, the one or more double strand breaks are repaired to create an altered sequence comprising insertions, deletions, base alterations, or a combination thereof.

In some embodiments, the base editor creates one or more base changes or small insertions/deletions in the endogenous copy of the essential gene.

In some embodiments, the one or more base changes comprise one or more point mutations, or deamidated bases that are replaced with nucleotides of a different sequence.

In some embodiments the Search and Replace Prime editor creates one or more base changes or insertion/deletions in the endogenous copy of the essential gene.

In some embodiments, the altered organism is heterozygous or homozygous for the vector or vectors.

In some embodiments, the organism is haploid. Non-limiting example of haploid organisms include prokaryotes. In some embodiments, the organism is diploid. Non-limiting example of diploid organisms include insects, fungi, many plants and animals. In some embodiments, the organism is polyploidy. Non-limiting examples of polyploid organisms include some fungi and animals and many plants.

In some embodiments, the organism is selected from the group consisting of prokaryotes, fungi, plants, and animals. In some embodiments, the organism is, without limitations, a prokaryote (bacteria, archaea), fungi, insect, mammal, rodent, fish, amphibian, reptile or plant. In some embodiments, any of the embodiments of the vectors and and/or methods can be one or more of the following: Autographa gamma Silver Y moth Chilo suppressalis Asiatic rice borer Diabrotica speciosa Cucurbit beetle Harpophora maydis Late wilt of corn Helicoverpa armigera Old world bollworm Heteronychus arator Black maize beetle Peronosclerospora maydis Java downy mildew Peronosclerospora philippinensis Philippine downy mildew Punctodera chalcoensis Mexican corn cyst nematode Sclerophthora rayssiae var. zeae Brown stripe downy mildew Spodoptera littoralis Egyptian cottonworm Spodoptera litura Cotton cutworm Thaumatotibia leucotreta False codling moth Anthonomus grandis Boll weevil Autographa gamma Silver Y moth Eutetranychus orientalis Citrus brown mite Helicoverpa armigera Old World bollworm Oxycarenus hyalinipennis Cotton seed bug Pectinophora gossypiella Pink bollworm Spodoptera littoralis Egyptian cottonworm Spodoptera litura Cotton cutworm Thaumatotibia leucotreta False codling moth Adoxophyes orana Summer fruit tortrix moth Aeolesthes sarta City longhorned beetle Agrilus biguttatus Oak splendour beetle Archips xylosteanus Variegated golden tortrix Epiphyas postvittana Light brown apple moth Lymantria dispar asiatica Asian gypsy moth Lymantria mathura Rosy moth Massicus raddei Mountain oak longhorned beetle Phytophthora quercina Oak decline Platypus quercivorus Oak ambrosia beetle Raffaelea quercivora Japanese oak wilt Scolytus intricatus European oak bark beetle Spodoptera littoralis Egyptian cottonworm Thaumatotibia leucotreta False codling moth Thaumetopoea processionea Oak processionary moth Tortrix viridana Green oak tortrix Tremex fuscicornis Tremex woodwasp Candidatus Phytoplasma pini Pine witches' broom Cronartium flaccidum Scots pine blister rust Dendroctonus micans Great spruce bark beetle Dendrolimus pini Pine-tree lappet Dendrolimus punctatus Masson pine moth Dendrolimus sibiricus Siberian silk moth Diprion pini Pine sawfly Hylobius abietis Large pine weevil Lymantria mathura Rosy moth Monochamus saltuarius Japanese pine sawyer Monochamus sutor Small white-marmorated longhorned beetle Mycosphaerella gibsonii Needle blight of pine Panolis flammea Pine beauty moth Tomicus destruens No common name, a pine shoot beetle Autographa gamma Silver Y moth Cernuella virgate Maritime garden snail Cochlicella spp. Exotic species Diabrotica speciosa Cucurbit beetle Helicoverpa armigera Old world bollworm Heterodera filipjevi Cereal cyst nematode Heterodera latipons Mediterranean cereal cyst nematode Heteronychus arator Black maize beetle Lobesia botrana European grape vine moth Meloidogyne artiellia British root-knot nematode Nysius huttoni Wheat bug Peronosclerospora philippinensis Philippine downy mildew Spodoptera littoralis Egyptian cottonworm Spodoptera litura Cotton cutworm Adoxophyes orana Summer fruit tortrix moth Alectra vogelii Yellow witchweed Autographa gamma Silver Y moth Cernuella virgata Maritime garden snail Chrysodeixis chalcites Golden twin spot moth Crocidosema aporema Bud borer Diabrotica speciosa Cucurbit beetle Eutetranychus orientalis Citrus brown mite Helicoverpa armigera Old world bollworm Spodoptera littoralis Egyptian cottonworm Adoxophyes orana Summer fruit tortrix moth Autographa gamma Silver Y moth Candidatus Phytoplasma australiense Australian grapevine yellows Cryptoblabes gnidiella Epiphyas Honeydew moth postvittana Eupoecilia ambiguella Candidatus Phytoplasma vitis 1 Light brown apple moth Heteronychus arator Lobesia botrana Pseudopezicula tracheiphila Spodoptera European grape berry moth littoralis Spodoptera litura Thaumatotibia leucotreta Flavescence doree Black maize beetle European grape vine Bursaphelenchus cocophilus Red ring nematode Candidatus Phytoplasma palmae Palm lethal yellowing Cocadviroid Coconut cadang cadang Coconut cadang cadang viroid Darna pallivitta Nettle caterpillar Haplaxius crudus American palm cixiid Metamasius hemipterus West Indian cane weevil Oryctes rhinoceros Coconut rhinoceros beetle Paysandisia archon No common name, a palm borer Raoiella indica Red palm mite Rhabdoscelus obscurus New Guinea sugarcane weevil Rhynchophorus ferrugineus Red palm weevil Rhynchophorus palmarum South American palm weevil Autographa gamma Silver-Y moth Candidatus Phytoplasma australiense Australian grapevine yellows Chrysodeixis chalcites Golden twin spot moth Globodera pallida Pale cyst nematode Globodera rostochiensis Golden nematode Helicoverpa armigera Old world bollworm Meloidogyne fallax False Columbia root-knot nematode Meloidogyne minor Root-knot nematode Neoleucinodes elegantalis Tomato fruit borer Ralstonia solanacearum race 3 Bacterial wilt/Southern biovar 2 bacterial Wilt Spodoptera littoralis Egyptian cottonworm Spodoptera litura Cotton cutworm Synchytrium endobioticum Potato wart Tecia solanivora Guatemalan potato tuber moth Thaumatotibia leucotreta False codling moth Tuta absoluta Tomato leaf miner Adoxophyes orana Summer fruit tortrix Argyresthia pruniella Cherry blossom moth Bactrocera zonata Peach fruit fly Candidatus Phytoplasma prunorum European stone fruit yellows Enarmonia formosana Cherry bark tortrix Epiphyas postvittana Light brown apple moth Grapholita funebrana (Syn.: Plum fruit moth Cydia funebrana) Leucoptera malifoliella Pear leaf blister moth Lobesia botrana European grape vine moth Monilia polystroma Asiatic brown rot Monilinia fructigena Brown rot, Apple brown rot Potyvirus Plum Pox Virus Plum pox Rhagoletis cerasi European cherry fruit fly Thaumatotibia leucotreta False codling moth Globodera pallida Pale cyst nematode Globodera rostochiensis Golden nematode Heterodera cajani Pigeonpea cyst nematode Heterodera ciceri Chickpea cyst nematode Heterodera filipjevi Cereal cyst nematode Heterodera latipons Mediterranean cereal cyst nematode Heterodera sacchari Sugarcane cyst nematode Punctodera chalcoensis Mexican corn cyst nematode Agrilus auroguttatus Goldspotted oak borer Agrilus biguttatus Oak splendour beetle Agrilus planipennis Emerald ash borer Anoplophora chinensis Citrus longhorned beetle Anoplophora glabripennis Asian longhorned beetle Chlorophorus annularis Bamboo borer Chlorophorus strobilicola Slender-banded pine cone longhorn beetle Dendroctonus micans Great spruce bark beetle Ips sexdentatus Six-toothed bark beetle Ips typographus European spruce bark beetle Megaplatypus mutatus No common name, an ambrosia beetle Monochamus alternatus Japanese pine sawyer Monochamus saltuarius Japanese pine sawyer Monochamus sutor Small white-marmorated longhorned beetle Orthotomicus erosus Mediterraneran pine engraver Pityogenes chalcographus Sixtoothed spruce bark beetle Platypus quercivorus Oak ambrosia beetle Scolytus intricatus European oak bark beetle Tetropium castaneum Black spruce beetle Tetropium fuscum Brown spruce longhorned beetle Tomicus destruens No common name, a pine shoot beetle Tomicus minor Lesser pine shoot beetle Tomicus piniperda Pine shoot beetle Trichoferus campestris Velvet longhorned beetle Trypodendron European hardwood ambrosia beetle domesticum Redbay ambrosia beetle Belocaulus spp. No common name, leatherleaf slugs Cernuella spp. No common name, hygromiid snails Cochlicella spp. No common name, cochlicellid snails Colosius spp. No common name, leatherleaf slugs Laevicaulis spp. No common name, leatherleaf slugs Lissachatina fulica Giant African snail Meghimatium pictum Chinese slug Monacha spp. No common name, hygromiid snails Sarasinula spp. No common name, leatherleaf slugs Semperula spp. No common name, leatherleaf slugs Veronicella spp. No common name, leatherleaf slugs Dendrolimus pini Pine-tree lappet Dendrolimus punctatus Masson pine moth Dendrolimus sibiricus Siberian silk moth Lymantria albescens Okinawa gypsy moth Lymantria dispar asiatica Asian gypsy moth Lymantria dispar japonica Japanese gypsy moth Lymantria mathura Rosy moth Lymantria monacha Nun moth Lymantria postalba White-winged gypsy moth Lymantria umbrosa Hokkaido gypsy moth Lymantria xylina Casuarina tussock moth.

In some embodiments, an insect can be a direct pest or indirect pest. A “direct pest” refers to insects that can cause damage at one or more stage of their life cycle by, for example, eating crops or damaging animals. The New World screw-worm fly Cochliomyia hominivorax, for example, is a direct pest of cattle, and the spotted wing Drosophila, Drosophila suzukii is pest of many fruit crops. An “indirect pest” refers to insects that transmit human diseases, for example, mosquitoes which carry malaria. Indirect pests of organisms other than humans, such as livestock or plants are also known.

In some embodiments, insect refers to, without limitations, one or more of Drosophila, mosquitoes, bumblebees, hoverflies, grasshoppers, dragonfly, dancefly, weevil, cricket, wasp, moth, beetles, honey bee, robberfly or butterfly. Additional examples of insects include, but are not limited to, Asian citrus psyllid (diaphorini citrii, Australian sheep blowfly (Lucilia cuprina, Asian tiger mosquito (Aedes albopictus); Japanese beetle (Popilla japonica), White-fringed beetle (Graphognatus spp.), Citrus blackfly (Aleurocanthus woglumi), Oriental fruit fly (Dacus dorsalis), Olive fruit fly (Dacus oleae), tropical fruit fly (Dacus cucurbitae, Dacus zonatus), Mediterranean fruit fly (Ceratitis capitata), Natal fruit fly (Ceratitis rosa), Chemy fruit fly (Rhagoletis cerasi), Queensland fruit fly (Bactrocera tryoni), Caribbean fruit fly (Anastrepha suspensa), imported fire ants (Solenopis richteri, Solenopis invictai, Gypsy moth (Lyman tria dispar), Codling moth (Cydia pomonella), Brown tail moth (Euproctis chrysorrhoea), yellow fever mosquito (Aedes aegypti), malaria mosquitoes (Anopheles gambiae, Anopheles stephensi), New world screwworm (Cochliomyia hominivorax), Old World Screwworm (Chrysomya bezziana), Tsetse fly (Glossina spp), Boll weevil (Anthonomous grandis), Damsel fly (Enallagma hageni), Dragonfly (Libellula luctuosa), and rice stem borer (Tryporyza incertulas). In some embodiments, the insect either transmits human disease or are agricultural pests. In some embodiments, the insects are wild insect populations.

In some embodiments, the insects are mosquitoes or flies (for example fruit flies, tsetse flies, sand flies). The mosquitoes can be, for example, Aedes sp. or Anopheles sp. In some embodiments, the mosquito is yellow fever mosquito (Aedes aegypti), malaria mosquito (Anopheles gambiae, Anopheles stephensi), Asian tiger mosquito (Aedes albopictus) or Culex mosquitoes. In some embodiments, the insect is one that transmits a disease of a mammal. The disease can be any disease, for example, malaria and/or yellow fever. In some embodiments, the insect is a Spotted wing Drosophila (Drosophila Suzukii).

In some embodiments, insect refers to an insect that spreads a disease of humans. In some embodiments, insect refers to an insect that spreads a disease of economically important animals. In some embodiments, insect refers to an insect that spreads a disease of companion animals. In some embodiments, insect refers to an insect that spreads a disease of plants.

In some embodiments, mosquitoes can be, without limitations, of Aedes, Anopheles, Culex, Coquillettidia, Haemagogus, Mansonia, Ochlerotatus, Psorophora or other genera that transmit diseases. In some embodiments, the diseases transmitted by mosquitoes can be one or more of Malaria, Chikungunya, Dog Heartworm, Dengue, Yellow Fever, Eastern Equine Encephalitis, St. Louis Encephalitis, LaCrosse Encephalitis, Western Equine Encephalitis, West Nile Virus, or Zika Virus, lymphatic filariasis.

In some embodiments, the population has about 10,000 to about 100,000,000,000 organisms. In some embodiments, the population has about 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, 10,000, 100,000, 500,000, 1,000,000, 100,000,000, 1,000,000,000, 100,000,000,000 or 1,000,000,000,000 organisms, or a number within a range defined by any two of the aforementioned values.

In some embodiments, the environment comprises an open environment, a bioreactor, or a multicellular body, a closed container, or combinations thereof. In some embodiments, the environment is a combination of an open environment, a bioreactor, or a multicellular body, a closed container, and the environment changes sequentially from one to the other

In some embodiments, the wild type organism is replaced at a high frequency with the altered organism in the population wherein the wild type organism is present. In some embodiments, the wild type organism is replaced at a high frequency with the altered organism in the population in a particular environment wherein the wild type organism is present. In some embodiments, high frequency is defined as replacement of at least 90% of the wild type organism with the altered organism after 50 generations. In some embodiments, high frequency is defined as replacement of at least 80% of the wild type organism with the altered organism after 50 generations. In some embodiments, high frequency is defined as replacement of at least 70% of the wild type organism with the altered organism after 50 generations. In some embodiments, high frequency is defined as replacement of at least 60% of the wild type organism with the altered organism after 50 generations. In some embodiments, high frequency is defined as replacement of at least 50% of the wild type organism with the altered organism after 50 generations.

In some embodiments, the wild type organism is replaced at a rapid rate with the altered organism in the population wherein the wild type organism is present. In some embodiments, the wild type organism is replaced at a rapid rate with the altered organism in the population in a particular environment wherein the wild type organism is present. In some embodiments, rapid rate is defined as replacement of at least 90% of the wild type organism with the altered organism after 50 generations. In some embodiments, rapid rate is defined as replacement of at least 80% of the wild type organism with the altered organism after 50 generations. In some embodiments, rapid rate is defined as replacement of at least 70% of the wild type organism with the altered organism after 50 generations. In some embodiments, rapid rate is defined as replacement of at least 60% of the wild type organism with the altered organism after 50 generations. In some embodiments, rapid rate is defined as replacement of at least 50% of the wild type organism with the altered organism after 50 generations.

In some embodiments, at least 90% of the wild type organism is replaced with the altered organism after 50 generations. In some embodiments, at least 90% of the wild type organism is replaced with the altered organism after 50 generations. In some embodiments, at least 80% of the wild type organism is replaced with the altered organism after 50 generations. In some embodiments, at least 70% of the wild type organism is replaced with the altered organism after 50 generations. In some embodiments, at least 60% of the wild type organism is replaced with the altered organism after 50 generations. In some embodiments, at least 50% of the wild type organism is replaced with the altered organism after 50 generations.

In some embodiments, the one or more sequence modifications in the one or more cells is a result of the one or more cells carrying the first gene encoding the DNA sequence modifying enzyme. In some embodiments, the one or more sequence modifications in the one or more cells is a result of the DNA sequence modifying enzyme being transmitted to the one or more cells from one or more cells expressing the DNA sequence modifying enzyme through diffusion following cell fusion. In some embodiments, the one or more sequence modifications in the one or more cells is a result of the DNA sequence modifying enzyme being transmitted to the one or more cells from one or more cells expressing the DNA sequence modifying enzyme through active transport. In some embodiments, the one or more sequence modifications in the one or more cells is a result of the one or more cells carrying the first gene encoding the DNA sequence modifying enzyme or a combination of genes that together encode the essential components of the DNA sequence modifying enzyme, and is a result of the DNA sequence modifying enzyme or its component parts being transmitted to the one or more cells from one or more cells expressing the DNA sequence modifying enzyme through diffusion following cell fusion, mating, or conjugation. In some embodiments, the one or more sequence modifications in the one or more cells is a result of the one or more cells carrying the first gene encoding the DNA sequence modifying enzyme and is a result of the DNA sequence modifying enzyme being transmitted to the one or more cells from one or more cells expressing the DNA sequence modifying enzyme through active transport. In some embodiments, the one or more sequence modifications in the one or more cells is a result of the DNA sequence modifying enzyme being transmitted to the one or more cells from one or more cells expressing the DNA sequence modifying enzyme or a combination of genes that together encode the essential components of the DNA sequence modifying enzyme through active transport and is a result of the DNA sequence modifying enzyme or its component parts being transmitted to the one or more cells from one or more cells expressing the DNA sequence modifying enzyme through active transport. In some embodiments, the one or more sequence modifications in the one or more cells is a result of the DNA sequence modifying enzyme being transmitted to the one or more cells from one or more cells expressing the DNA sequence modifying enzyme through intercellular movement which may occur through multiple mechanisms including conjugation, vesicle uptake, uptake of free enzyme, uptake of cell synthesized nanoparticles, uptake through tunneling nanotubes.

In some embodiments, the vector or vectors are positioned in one or more chromosomes or extra-chromosomal elements by a homologous recombination-dependent integration, random integration, integration using transposition, integration using a recombinase, or combinations thereof.

In some embodiments, the one or more cargo sequences comprise a one or more foreign gene sequences, or one or more alleles of an endogenous chromosomal or extra-chromosomal gene to which the vector has been linked through nearby insertion on the chromosome or extra-chromosomal element that carries the endogenous allele of interest.

In some embodiments, when the vector is positioned on the chromosome or the extra-chromosomal element, the first gene operably linked to the first promoter, the second gene operably linked to the second promoter, and the one or more cargo transgenes are genetically linked.

In some embodiments, when two vectors are utilized, these are positioned on distinct chromosomes or on the same chromosome at some distance with respect to each other, the first gene is operably linked to the first promoter, the second gene operably linked to the second promoter, the third gene operably linked to the third promoter, and the fourth gene operably linked to the fourth promoter, and the one or more cargo transgenes are in some cases genetically linked.

In some embodiments of single locus and two locus ClvR the separation of a functional Rescue from the Cargo can be prevented by locating the Cargo in an intron of the Rescue (FIG. 22). A break between the two genes followed by reciprocal end joining with the same region on the homologous chromosome could potentially separate them, though the frequency of this kind of event is unclear. Locating the ClvR cargo in an intron of the Rescue transgene (bottom panel) prevents breakage and end joining-mediated separation of a functional Rescue (the key component driven into the population by ClvR) from the Cargo. Separation could otherwise generate empty ClvR elements (ClvR^(Δcargo), top panel), or Rescue only elements (ClvR^(rescue), middle panel), the spread of which provide no beneficial function. Crossed lines indicate sites of chromosome breakage and end joining with a similar position on a homologous chromosome. Recombinant products of interest are indicated by the dotted lines.

In some embodiments of single and two locus ClvR separation of a functional Rescue from the Cargo can be prevented by locating the Cargo between two transgenes whose co-expression is required to produce a functional Rescue essential enzyme, such as dihydrofolate reducatse (FIG. 23). The 5′ half of DHFR is driven by its own promoter. The 3′ half is driven by a strong ubiquitous promoter. The two domains are brought together to form an active enzyme through heterodimerization, mediated by specific domains at the N-terminus of each protein (boxes with diagonal lines).

In some embodiments of single and two locus ClvR separation of a functional Rescue from the Cargo can be prevented by locating the Cargo between two transgenes whose co-expression is required to produce a functional Rescue protein (FIG. 24). Here this is achieved using a two-component transcription-based system. The essential gene promoter drives the expression of a heterologous transcriptional activator such as GAL4. The Rescue transgene contains GAL4 UAS binding sites sufficient to drive GAL4-dependent expression, upstream of an otherwise promoterless, recoded Rescue transgene.

In some embodiments of single and two locus ClvR Cas9 can be made essential for Rescue function. A circuit that selects against mutation of Cas9/gRNAs to inactivity is illustrated in FIG. 32. In this implementation a variant of Cas9 known as Cas9-VPR includes a domain that can activate transcription following DNA binding. Cas9-VPR can also bring about cleavage of full length target sites. Importantly, however, Cas9-VPR can also bind truncated gRNA target sites and drive transcription of a nearby gene, without cleaving these sites. In this way the exact same gRNAs and Cas9 are used for cleavage and transcriptional activation. The figure illustrates an implementation in which Cas9 expression is driven by the promoter of the essential gene. The gRNAs are expressed ubiquitously under U6 promoter control, as usual. Cas9 and gRNAs will cleave the wildtype copy of the essential gene in all tissues in which the essential gene is expressed. Cas9 and gRNAs will also drive expression of a promoterless, recoded version of the essential gene (the Rescue) in these same tissues. The system thus creates tight linkage between components required for cleavage and those required for rescue. It can fail due to point mutations in Cas9 that allow target site DNA binding and transcriptional activation but that prevent cleavage, as with dead Cas9 variants used for transcriptional regulation or visualization of specific genomic loci. These will happen, but are very specific mutations, and thus any spread of dead Cas9 within the population should be delayed. An important requirement for this approach is that the essential gene be expressed in the germline at levels sufficient to bring about Cas9-dependent germline cleavage of the wildtype essential gene. Also note that unless the essential gene is only required in the germline, Cas9 will be expressed and active in some somatic tissues.

In some embodiments of the method, the vector and cargo are located in a small chromosomal inversion. In some embodiments of the method, the vector and cargo are located in a small chromosomal inversion further limiting the possibility that the vector and cargo can separate from each other during any stage of DNA replication, mitosis, and/or or meiosis.

In some embodiments, the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene with a high cleavage efficiency. In some embodiments, the high cleavage frequency is defined as at least 30% of individuals carrying the nuclease cleave the endogenous copy of the essential gene in each generation. In some embodiments, the high cleavage frequency is defined as at least 40% of individuals carrying the nuclease cleave the endogenous copy of the essential gene being cleaved in each generation. In some embodiments, the high cleavage frequency is defined as at least 50% of individuals carrying the nuclease cleave the endogenous copy of the essential gene being cleaved in each generation. In some embodiments, the high cleavage frequency is defined as at least 60% of individuals carrying the nuclease cleave the endogenous copy of the essential gene being cleaved in each generation.

In some embodiments, the high cleavage frequency is defined as the nuclease cleaving one or more alleles of the endogenous copy of the essential gene in at least 30% of organisms carrying the vector or vectors and the one or more alleles of the endogenous copy of the essential gene in each generation. In some embodiments, the high cleavage frequency is defined as the nuclease cleaving one or more alleles of the endogenous copy of the essential gene in at least 40% of organisms carrying the vector or vectors and the one or more alleles of the endogenous copy of the essential gene in each generation. In some embodiments, the high cleavage frequency is defined as the nuclease cleaving one or more alleles of the endogenous copy of the essential gene in at least 50% of organisms carrying the vector and the one or more alleles of the endogenous copy of the essential gene in each generation. In some embodiments, the high cleavage frequency is defined as the nuclease cleaving one or more alleles of the endogenous copy of the essential gene in at least 60% of organisms carrying the vector or vectors and the one or more alleles of the endogenous copy of the essential gene in each generation.

In some embodiments, the base editor creates one or more base changes in endogenous copy of the essential gene with a high base editing frequency. In some embodiments, the high base editing frequency is defined as base editing in at least 20% of organisms that carry the vector or vectors in each generation. In some embodiments, the high base editing frequency is defined as base editing in at least 30% of organisms that carry the vector in each generation. In some embodiments, the high base editing frequency is defined as base editing in at least 40% of organisms that carry the vector or vectors in each generation. In some embodiments, the high base editing frequency is defined as base editing in at least 50% of organisms that carry the vector or vectors in each generation.

In some embodiments, the high base editing frequency is defined as the base editor modifying one or more alleles of the endogenous copy of the essential gene in at least 20% of the organisms carrying the vector or vectors and the one or more alleles of the endogenous copy of the essential gene in each generation. In some embodiments, the high base editing frequency is defined as the base editor modifying one or more alleles of the endogenous copy of the essential gene in at least 30% of the organisms carrying the vector or vectors and the one or more alleles of the endogenous copy of the essential gene in each generation. In some embodiments, the high base editing frequency is defined as the base editor modifying one or more alleles of the endogenous copy of the essential gene in at least 40% of the organisms carrying the vector or vectors and the one or more alleles of the endogenous copy of the essential gene in each generation. In some embodiments, the high base editing frequency is defined as the base editor modifying one or more alleles of the endogenous copy of the essential gene in at least 50% of the organisms carrying the vector or vectors and the one or more alleles of the endogenous copy of the essential gene in each generation.

In some embodiments of the method, the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene with a high cleavage efficiency. In some embodiments of the method, the high cleavage frequency is defined as the nuclease cleaving the endogenous copy of the essential gene in at least 30% of the organisms carrying the vector or vectors in each generation. In some embodiments of the method, the base editor creates one or more base changes in the endogenous copy of the essential gene with a high base editing frequency. In some embodiments of the method, the high base editing frequency is defined as the base editor modifying the endogenous copy of the essential gene in at least 20% of the organisms carrying the vector or vectors in each generation. In some embodiments of the method, the Search and Replace Prime editor nicks the target DNA in the endogenous copy of the essential gene, and reverse transcriptase, in conjunction with a modified gRNA, creates base changes, insertions or deletions, with high efficiency. In some embodiments of the method, the high frequency of modification is defined as modification of the endogenous copy of the essential gene at a frequency of at least 20% per gRNA of organisms carrying the vector, or progeny of these organisms, in each generation.

In some embodiments, the promoter of the first gene is a female-specific promoter such that the first gene encoding the DNA sequence modifying enzyme is expressed within females only. In some embodiments, female-specific expression of the DNA sequence modifying enzyme results in the DNA-modifying enzyme being present in the eggs. In some embodiments, when an egg expressing the DNA sequence modifying enzyme is fertilized by a male gamete, the DNA sequence modifying enzyme from the egg can modify target sequence in the paternal copy provided by the father. In some embodiments, there is paternal carryover wherein sperm contribute DNA modifying activity to eggs, resulting in modification of the copy of the target sequence provided by the mother. In some embodiments, there is potential for carryover. In some embodiments, modification of an allele in a fertilized egg is achieved even when the allele is inherited from a parent that did not carry the vector.

In some embodiments, the promoter of the first gene is a germline-specific promoter such that the first gene encoding the DNA sequence modifying enzyme or an essential component of this enzyme is expressed within the germline only. In some embodiments the promoter of the second gene, which drives expression of gRNAs, results in ubiquitous gRNA expression. In some embodiments, germline-specific expression of the DNA sequence modifying enzyme and the ubiquitously expressed gRNAs results in the DNA-modifying enzyme being present in the eggs through maternal carryover from oogenesis. In some embodiments, when an egg carrying the DNA sequence modifying enzyme deposited during oogenesis is fertilized by a male gamete, the DNA sequence modifying enzyme from the egg can modify target sequence in the paternal copy provided by the father. This is known as maternal carryover. In some embodiments, there is paternal carryover wherein sperm contribute DNA modifying activity to eggs, resulting in modification of the copy of the target sequence provided by the mother. In some embodiments, there is potential for carryover. In consequence, in some embodiments, modification of an allele in a fertilized egg is achieved even when the allele is inherited from a parent that did not carry the vector.

In some embodiments, as used herein, “fitness cost” is defined as a relative reduction in the number of offspring produced by, or survival of, individuals carrying the transgenic construct, as compared with wild type individuals. In some embodiments fitness cost is defined as a relative reduction in the number of offspring produced by, or survival of, individuals not carrying the transgenic construct, as compared with those who do. In some embodiments, fitness benefit is defined as a relative increase in the number of offspring produced by, or survival of, individuals carrying the transgenic construct as compared with wild type individuals.

In some embodiments, the first gene expresses within females (the female germline or cells that contribute components to the female germline), such that the DNA-modifying enzyme and any associated cofactors such as guide RNAs, whose expression may be driven by an independent promoter, are deposited into all oocytes/eggs, including those that do not inherit one or more of the vectors, and modify target sequences in the version of the essential gene provided by the father. This represents maternal carryover of DNA sequence modifying activity.

In some embodiments, paternal carryover of the DNA modifying enzyme results in modification of the maternal copy of the essential locus in eggs, including those that do not inherit the vector or vectors.

Applications

In some embodiments, the methods provided herein can be applied for modification of populations for beneficial outcomes. For example, in some embodiments, to prevent mosquito-borne diseases (e.g., malaria, dengue, etc.), mosquitoes can be engineered based on the embodiments of the vectors and methods disclosed herein to resist infection. The engineered mosquito can be used to replace wild mosquito population in order to achieve less transmission and less disease. Such a trait (e.g., refractoriness of the engineered mosquito to disease transmission) is unlikely to spread into a population in the absence of gene drive because the trait results in a fitness cost to carriers. A gene drive solution to this problem described herein is to increase the fitness cost associated with not carrying the gene of interest through DNA sequence modification-based gene drive.

In comparison to other low threshold gene drive systems (Example, 12-14), the single locus Cas9 based gene drive mechanisms in Examples 1-11, Examples 15-17, Example 24, Examples 30-39 do not require any homing to occur (homing is known to vary in its relative rate compared to other forms of DNA repair in different species), and they are predicted to rapidly take over wild type populations even when the associated cargo results in significant fitness costs. The presently proposed DNA sequence modification-based drives, including two locus versions of ClvR in Examples 15-19 (FIGS. 34A-F, FIGS. 35A-F), are all predicted to replace wild type populations quickly while bearing substantial fitness costs, and each of the these drives displays characteristics that qualify them for different scenarios.

While all of these single and two locus ClvR drive mechanisms have been considered in the context of Cas9, these drive results could apply to any endonuclease or base editor used or Search and Replace Prime editor or other method of bringing about site-specific modification of DNA, used to disrupt the function of an endogenous gene. For some embodiments, one of the biggest advantages of these drives is their adaptability to new species. This is because the primary requirements are the identification of an essential gene (thousands in each organism), a recoded or sequence unrelated version of the gene (including associated regulatory sequences) that has wildtype or close to wildtype function, and a promoter and DNA sequence-modifying enzyme capable of bringing about sequence alteration of the endogenous copy of the essential gene in the germline, or germline and early embryo cells exposed to the enzyme.

ADDITIONAL EMBODIMENTS

Without being limited by any particular theory, one implementation of a DNA sequence-based modification-based gene drive is as follows: a cell expresses a DNA sequence modifying enzyme that alters the sequence of an essential gene, inactivating it. The DNA sequence modifying enzyme is transmitted through cytoplasm to offspring (either maternally, paternally, or both), where it modifies the target gene, regardless of whether the gene encoding the DNA sequence modifying enzyme is transmitted to these progeny. Progeny that inherit the DNA sequence modifying enzyme-encoding gene also inherit a rescue copy of the wildtype gene that has been cleaved. This rescue copy is both functional and uncleavable. In this way key features required for gene drive are brought about in both single and two locus configurations.

Without being limited by any particular theory, some embodiments of a DNA sequence-based modification-based gene drive are as follows: a cell expresses a DNA sequence modifying enzyme—or a first component of this enzyme such that when a first and second components are both present—that alters the sequence of an essential gene, inactivating it. The DNA sequence modifying enzyme is transmitted through cytoplasm to offspring (either maternally, paternally, or both), where it modifies the target gene, regardless of whether the gene or genes encoding the DNA sequence modifying enzyme is transmitted to these progeny. Progeny that inherit the DNA sequence modifying enzyme-encoding gene or a first component of it have some probability, depending on the degree of linkage with the Rescue and any associated transgenes, to also inherit a Rescue copy of the wildtype gene that has been cleaved. This Rescue copy is both functional and uncleavable. Since one or more components of the gene or gene encoding the DNA sequence modifying enzyme have a non-zero frequency of recombination (up to 50%) with the rescue, the genes encoding one or more components of the DNA sequence modifying enzyme will sometimes find themselves in individuals who lack the rescue and any other functional copies of the essential gene. These individuals die. Since drive requires the creation of LOF alleles by the DNA sequence modifying enzyme, drive in the presence of recombination will decrease over generations, and ultimately cease. In this way, key features required for transient gene drive are brought about. If the rescue and/or any associated transgenes, or components of the DNA sequence modifying enzyme result in a fitness cost to carriers, dilution of the population with wildtypes, in the absence of drive, or in the presence of low levels of drive, can lead to loss of transgenes from the population. In this way key features required for reversible gene drive are brought about.

In some embodiments, the above system is applicable to insects. A DNA sequence modifying enzyme is expressed under the control of a germline promoter. The promoter may be expressed in both the male and female germline. However, let us also consider a case in which the nuclease is expressed under the control of a late female germline specific promoter. In this case the DNA sequence modifying enzyme is transmitted from the oocyte, where its mRNA (and any associated co-factors such as gRNAs) is synthesized, to the mature oocyte/fertilized egg. In the zygote (fertilized egg) the DNA sequence modifying enzyme alters wildtype copies of the gene, resulting in their inactivation. This inactivation can occur in the nuclei that will ultimately give rise to cells of various somatic tissues of the animal. It can also occur in the cells that will give rise to the embryonic germline. Without being limited by any particular theory, provided that endogenous copies of the essential gene are altered in a sufficient number of nuclei, and are inactivated in both copies (for diploid organisms), which can happen early in embryogenesis (at the single diploid nucleus stage) or later, after some number of nuclei have been generated, then development will be disrupted, resulting in animal death. However, if the zygote inherits along with the DNA sequence modifying enzyme-encoded gene a tightly linked copy of the rescue transgene that cannot be modified, or copy of the rescue transgene that is not tightly linked to that of the DNA sequence modifying enzyme, progeny will survive if they inherit the rescue transgene, even if both copies of the wildtype copy of the gene have been modified. This occurs because for most genes in diploids heterozygosity for one wildtype copy of the gene is sufficient to provide enough function to allow the organisms to survive and thrive. Good evidence for this conclusion comes from several sources: the many examples of phenotypically normal heterozygotes in many species; and the ability to create and maintain healthy stocks for deletions that eliminate, one at a time, one copy of most regions of the drosophila genome (flybase.org). If there is a modest fitness cost associated with heterozygosity this will be decreased over time as the construct spreads. This is because as spread occurs the frequency of homozygotes for the construct rises, in which case individuals now carry two copies of the rescue gene of interest and are therefore have increased fitness. Importantly, there is no requirement that the essential gene being targeted is haplosufficient or even haploviable. This is illustrated in FIGS. 31C and D, which show predicted drive behavior when a haplolethal (heterozygotes are dead) gene is targeted.

Without being limited by any particular theory, the model can be generalized and extrapolated to prokaryotes or other haploids carrying a plasmid that encodes a DNA sequence modifying enzyme and a recoded or sequence unrelated version of an essential gene. In this case progeny that fail to inherit the plasmid will still inherit the chromosomal mutation that results in loss of function of the wildtype copy of the gene. They may also inherit the DNA sequence modifying enzyme, in which case the sequence of any wildtype copies of the essential gene (incorporated through horizontal gene transfer, transduction, transformation, or conjugation) will be altered and the cell will die. However, those cells that inherit the plasmid inherit a functional copy of the gene, even though the chromosomal version of the gene has been altered (FIG. 6; FIG. 43).

Without being limited by any particular theory, the model can be generalized and extrapolated to organisms such as yeast, other fungi and some plants that go from a haploid to diploid phase and back to haploid through sporulation or have a prolonged gametophyte stage in which transcription of the essential gene is required for haploid stage or gamete viability. A chromosomal copy of the DNA sequence modifying enzyme and a recoded or sequence unrelated version of the rescue will be transmitted to only some progeny during sporulation. Those haploids that fail to inherit the rescue copy of the gene will die because the DNA sequence modifying enzyme, which is transmitted through cytoplasm, will cause alteration of the wildtype copy. The wildtype copy of the gene will likely also have been cleaved during the diploid stage in which case cytoplasmic inheritance of the nuclease is not essential. In any case, only haploids that inherit the tightly linked rescue construct, or rescue construct separated by some degree of linkage from that encoding the DNA sequence modifying enzyme, will survive. This constitutes a kind of gamete killing (FIG. 10). Most generally, the system described applies to any biological situation in which a DNA sequence modifying enzyme alters the sequence of an essential gene so as to disrupt essential functions in haploid, diploid or polyploid cells. This modification can occur in the parental cell, which can be haploid, diploid, tetraploid, or polyploid. Alternatively the DNA sequence modifying enzyme, the transcript and/or protein for which is produced in the parental cell, can alter the sequence of the essential gene in the progeny cells in which it becomes located through cytoplasmic diffusion or active transport. The operative principle in all cases is that in the relevant cell type, or in a multicellular organism, in some fraction of these cells, all or most copies of the endogenous copies of the essential gene are altered so as to produce non-functional copies of the gene. This results in death of all cells that fail to inherit one or more copies of the rescue transgene. The DNA sequence modifying enzyme and the rescue transgene are tightly linked and behave as a single genetic unit. As described herein, this same set of principles applies to two locus versions of ClvR. In such systems those cells inheriting the Rescue and any other associated cargo will survive, while those that do not (including those who inherit some or all components of the DNA sequence modifying enzyme) will die.

In some embodiments, the model is extrapolated to a diploid animal such as a rodent, mosquito, fish, amphibian, a plant or other organism in which spermatogenesis (pollen formation and/or function) utilizes haploid-specific promoters to drive the expression of genes essential for spermatogenesis (pollen formation/function). In some embodiments, the DNA sequence modifying enzyme is expressed in the germline at some point. It is not critical when, or in which sex. What matters is that ultimately one will end up with post-meiotic cells that carry a copy of the rescue transgene, while their post-meiotic brothers do not. To the extent that it is true that the product of the rescue transgene, which will have all the endogenous regulatory sequences of the endogenous gene, does not diffuse into the meiotic brothers to which they are still connected by cytoplasmic bridges, those sperm will die, be resorbed, or be ejaculated in a state that is non-functional. This will result in nuclease and rescue transgene-bearing meiotic products being preferentially represented in the next generation, a form of population replacement.

In some embodiments, a rescue version of a post-meiotic expressed gene that is normally present on an autosome can be expressed from the Y chromosome along with the DNA sequence modifying enzyme. Provided the DNA sequence modifying enzyme alters the wildtype endogenous copy of the gene in the germline then only Y-bearing sperm will generate this product. This holds even if the haplo-expressed gene is on the autosome (FIG. 11). In early generations there may be some reduced sex ratio bias if some wildtype copies are not cleaved, and depending on when in germline development the nuclease acts (before or after this generations post-meiotic expression). However, the bottom line is the same. Eventually, wildtype copies of the haplo-expressed gene are lost and the only remaining functional copies are those on the Y chromosome. This can result in sex ratio distortion if the sperm in which the gene has been inactivated are unable to carry out fertilization.

In some embodiments, the model is applicable to species with ZW sex chromosomes. W is the sex chromosome. Males are ZZ. A W chromosome that carries a rescue cassette and a nuclease. It is inherited only into females. Males that inherit the Z chromosome inherit a cleaved copy of an essential Z gene, or cleaved copies of an autosomal essential gene. In any case, ultimately a population in which there are only females is obtained because males do not inherit a rescue construct. Eggs that are genotypically male simply do not develop. A big male egg is still obtained because the actual embryo is quite small. However, viable individuals are not obtained. Ultimately females carrying the rescue construct and no wildtype copies of the gene are mated with wildtype males. Female progeny survive. Male progeny do not survive if there is maternal carryover that causes killing of the wildtype loci inherited from the male. If W-bearing females are mated with to wildtype males, which is what is done in a breeding or hybrid generation situation, the males will all die if the gene that is essential is normal on the Z and there is enough maternal carryover of the DNA sequence modifying enzyme to cause the wildtype copy of whatever chromosome carries the wildtype copy of the gene from males to undergo sequence modification such that males inherit no good copies of the essential gene.

In some embodiments, a vector is provided. In some embodiments, the vector comprises a first gene encoding a DNA sequence modifying enzyme, wherein the DNA modifying enzyme modifies an endogenous copy of an essential gene, a first promoter operably linked to the first gene encoding the DNA sequence modifying enzyme, a second gene encoding a rescue transgene, a second promoter operably linked to the rescue transgene, and optionally, one or more cargo sequences, wherein the vector is configured to be positioned in a chromosome or an extra-chromosomal element.

In some embodiments two vectors are provided, with each vector containing distinct parts of the vector described in FIG. 20A and illustrated in FIG. 49A, in Example 40. In some embodiments the first vector comprises a first gene encoding a DNA sequence modifying enzyme, wherein the DNA sequence modifying enzyme modifies an endogenous copy of an essential gene, and a promoter is operably linked to the first gene encoding the DNA sequence modifying enzyme, wherein the vector is configured to be positioned in a chromosome or extra chromosomal element. In one embodiment the second vector encodes a rescue transgene, a second promoter operably linked to the rescue transgene, and optionally, one or more cargo sequences, wherein the vector is configured to be positioned in a chromosome or an extra-chromosomal element at some distance from the first vector encoding the DNA sequence modifying enzyme on the same chromosome or extra chromosomal element, or on a distinct chromosome or extra chromosomal element. Distance is defined in terms of probability of recombination between the two vectors during each replication cycle or generation, with 50 map units or greater (50% probability of recombination) being equivalent independent segregation.

In some embodiments two vectors are provided, with each vector containing distinct parts of the vector described in FIG. 20A. In some embodiments the first vector comprises a first gene encoding a first component of a DNA sequence modifying enzyme, wherein the complete DNA sequence modifying enzyme modifies an endogenous copy of an essential gene, and a promoter is operably linked to the first gene encoding first component of a DNA sequence modifying enzyme, wherein the vector is configured to be positioned in a chromosome or extra chromosomal element. In some embodiments the second vector encodes a second component of a DNA sequence modifying enzyme, a promoter operably linked to the second component, a rescue transgene, a second promoter operably linked to the rescue transgene, and optionally, one or more cargo sequences, wherein the vector is configured to be positioned in a chromosome or an extra-chromosomal element at some distance from the first vector encoding the first component of the DNA sequence modifying enzyme on the same chromosome or extra chromosomal element, or on a distinct chromosome or extra chromosomal element. Distance is defined in terms of probability of recombination between the two vectors during each replication cycle or generation, with 50 map units or greater (50% probability of recombination) being equivalent independent segregation. See FIGS. 20A-D and FIGS. 21A-C.

In some embodiments of the vector, the DNA sequence modifying enzyme is a nuclease, a base editor, or a Search and Replace Prime editor. In some embodiments of the vector, the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene. In some embodiments of the vector, the one or more double strand breaks are repaired to create an altered sequence of the essential gene. In some embodiments of the vector, the base editor creates one or more base changes in the endogenous copy of the essential gene to create an altered sequence of the essential gene. In some embodiments of the vector, the one or more base changes comprise one or more point mutations in the endogenous copy of the essential gene. In some embodiments of the vector, the Search and Replace Prime editor creates one or more base changes, or insertions, or deletions, in the endogenous copy of the essential gene to create an altered sequence of the essential gene.

In some embodiments of the vector, the rescue transgene is either a recoded copy of the essential gene or is a gene of unrelated sequence, wherein the rescue transgene encodes a protein that is functionally equivalent to a protein encoded by the essential gene, and wherein the DNA sequence modifying enzyme does not modify the rescue transgene.

In some embodiments of the vector, the chromosome is an autosome, X chromosome, Y chromosome, Z chromosome, W chromosome, or supernumerary chromosome. In some embodiments of the vector, the extra-chromosomal element is a plasmid or a virus.

In some embodiments of the vector, the one or more cargo sequences comprise one or more foreign gene sequences, or one or more alleles of an endogenous chromosomal or extra-chromosomal gene to which the vector has been linked through nearby insertion on the chromosome or extra-chromosomal element that carries the endogenous allele of interest.

In some embodiments of the vector, the vector is positioned within a gene required for fertility or viability.

In some embodiments of the vector, the DNA sequence modifying enzyme is selected from the group consisting of Cas9, Cas-9-related RNA-guided nucleases, ZFN, TALEN, homing endonuclease, restriction enzymes, natural site-specific nucleases, engineered site-specific nucleases, base editing enzymes, transposase, Search and Replace Prime editing enzyme complex cytidine deaminase, and adenine deaminase.

In some embodiments, the vector further comprises one or more additional sequences, wherein the one or more additional sequences allow the vector to be positioned in the chromosome or the extra-chromosomal element. In some embodiments of the vector, the one or more additional sequences is selected from the group consisting of transposase binding site, LTRs, recombinase binding site, a sequence with homology to a desired location on the chromosome or the extra-chromosomal element.

In some embodiments of the vector, the first promoter is selected from the group consisting of a germline promoter, a male specific germline promoter, a female specific germline promoter, a cell-type specific promoter, a tissue-specific promoter, a ubiquitous promoter, a promoter activated at a specific stage of mitosis, and a promoter activated at a specific stage of meiosis.

In some embodiments of the vector, the double strand break is repaired by a mechanism selected from the group consisting of non-homologous end joining, microhomology-mediated end joining, and incomplete homologous recombination.

In some embodiments of the vector, the size of the one or more cargo sequences ranges from about 0.5 kb to about 500 kb.

In some embodiments of the vector, the nuclease comprises at least one nuclease domain and one or more DNA binding domains. In some embodiments of the vector, when the nuclease is Cas9 or a Cas9-related enzyme, the vector further comprise one or more genes encoding a guide RNA, wherein the guide RNA enables the nuclease to target specific sequences within the essential gene through Watson-Crick base pairing. In some embodiments of the vector, when the nuclease is Cas9, the nuclease domain of Cas9 is inactivated through one or more mutations, and the vector comprises a different nuclease domain. In some embodiments of the vector, the different nuclease domains is a single chain variant of FokI. In some embodiments of the vector, when the DNA binding domain is a TALE, the nuclease domain is provided as a single active nuclease domain, such as single chain variants of FokI.

In some embodiments of the vector, the Rescue and the Cargo transgenes are arranged such that the Cargo is located in an intron of the Rescue transgene (FIG. 22).

In some embodiments of the vector the cargo is located between two transgenes whose co-expression is required to create a functional Rescue protein (FIG. 23).

In some embodiments of the vector, the Rescue and the Cargo transgenes are arranged such that the Cargo is located between two transgenes, the presence of both of which is required for expression of a functional Rescue transgene (FIG. 24).

In some embodiments, a method of modifying a population by a vector is provided. In some embodiments, the method comprises obtaining an organism of the population, positioning one or more vectors, configured to be positioned in at least one chromosome or extra-chromosomal element in the organism, comprising a first gene encoding a DNA sequence modifying enzyme or first component thereof, wherein the DNA modifying enzyme modifies an endogenous copy of an essential gene, a first promoter operably linked to the first gene encoding the DNA sequence modifying enzyme or first component thereof, a second gene encoding a rescue transgene, a second promoter operably linked to the rescue transgene, optionally a third promoter operably linked to second component of the DNA sequence modifying enzyme, and optionally, one or more cargo sequences, expressing the DNA sequence modifying enzyme in the organism, inducing one or more sequence modifications in the essential gene in one or more cells in the organism, such that the one or more sequence modifications result in the essential gene being rendered partially or wholly non-functional and result in a defect in survival, growth control, fertility, or differentiation of the one or more cells if the one or more cells lack the rescue transgene, rescuing the defects in survival, growth control, or differentiation of the one or more cells in which the essential gene has been rendered partially or wholly non-functional, by the rescue transgene, generating an altered organism, wherein the altered organism carries one or more copies of the vector, and wherein the defects in survival, growth control, or differentiation of the one or more cells in which the essential gene has been rendered partially or wholly non-functional have been rescued by the rescue transgene, introducing the altered organism in an environment wherein an increase in a frequency of the altered organism is desired relative to a frequency of a wild type organism in the population; replacing the wild type organism with the altered organism in the population in the environment wherein the altered organism is introduced, thereby modifying the population.

In some embodiments of the method, an organism with the defect in survival, growth control, fertility, or differentiation of the one or more cells is eliminated if the one or more cells of the organism lack the rescue transgene.

In some embodiments of the method, the DNA sequence modifying enzyme does not modify the rescue transgene.

In some embodiments of the method, rescuing the defects in survival, growth control, or differentiation is achieved by restoring normal survival, growth control, fertility, or differentiation of the one or more cells by the rescue transgene.

In some embodiments of the method, the one or more cells comprise prokaryotic cells, somatic cells, germline cells, gametes, or a combination thereof.

In some embodiments of the method, the DNA sequence modifying enzyme is a nuclease, a base editor, or a Search and Replace Prime editor. In some embodiments of the method, the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene.

In some embodiments of the method, the one or more double strand breaks are repaired to create an altered sequence comprising insertions, deletions, base alterations, or a combination thereof.

In some embodiments of the method, the one or more double strand breaks are repaired to create an altered sequence using a previously cleaved and altered uncleavable sequence on a homologous chromosome as a template for repair mediated by homologous recombination (FIG. 6).

In some embodiments of the method, the base editor creates one or more base changes or small insertions/deletions in the endogenous copy of the essential gene. In some embodiments of the method, the one or more base changes comprise one or more point mutations, or deamidated bases that are replaced with nucleotides of a different sequence.

In some embodiments of the vector, the Search and Replace Prime editor creates one or more base changes, or insertions, or deletions, in the endogenous copy of the essential gene to create an altered sequence of the essential gene.

In some embodiments of the method, the altered organism is heterozygous or homozygous for one or more of the vectors. In some embodiments of the method, the organism is haploid, diploid, or polyploid. In some embodiments of the method, the organism is selected from the group consisting of prokaryotes, fungi, plants, and animals,

In some embodiments of the method, the environment comprises an open environment, a bioreactor, a multicellular body, or a colony of individual cells.

In some embodiments of the method, the wild type organism is replaced at a high frequency with the altered organism carrying one or more of the vectors in the environment wherein the wild type organism is present. In some embodiments of the method, the high frequency is defined as replacement of at least 90% of the wild type organism with the altered organism after 100 generations in the population. In some embodiments of the method, the wild type organism is replaced at a rapid rate with the altered organism in the environment wherein the wild type organism is present. In some embodiments of the method, the rapid rate is defined as replacement of at least 90% of the wild type organisms by organisms carrying the vector in the population after at most 100 generations.

In some embodiments of the method, the one or more sequence modifications in the one or more cells is a result of the one or more cells carrying the first gene encoding the DNA sequence modifying enzyme or is a result of the DNA sequence modifying enzyme being transmitted to the one or more cells from one or more cells expressing the DNA sequence modifying enzyme through diffusion, active transport, or movement of the DNA sequence modifying enzyme from a cell that expresses the DNA sequence modifying enzyme to a cell that does not express the DNA sequence modifying enzyme. (FIG. 6, 7; FIG. 9A; FIG. 10, 11; FIG. 26, FIG. 43..

In some embodiments of the method, one or more of the vectors is positioned on the chromosome or the extra-chromosomal element by a homologous recombination-dependent integration. In some embodiments of the method, one or more of the vectors is positioned on the chromosome or extra-chromosomal element by random integration, integration using transposition, integration using a recombinase, or a combination thereof.

In some embodiments of the method, the one or more cargo sequences comprise one or more foreign gene sequences, or one or more alleles of an endogenous chromosomal or extra-chromosomal gene to which the vector has been linked through nearby insertion on the chromosome or extra-chromosomal element that carries the endogenous allele of interest.

In some embodiments of the method, the vector is positioned on the chromosome or the extra-chromosomal element, the first gene operably linked to the first promoter, the second gene operably linked to the second promoter, and the one or more cargo transgenes are genetically linked.

In some embodiments of the method, the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene with high cleavage efficiency. In some embodiments of the method, the high cleavage frequency is defined as the nuclease cleaving the endogenous copy of the essential gene in at least 30% of the organisms carrying the vector and the endogenous copy of the essential gene in each generation. In some embodiments of the method, the base editor creates one or more base changes in the endogenous copy of the essential gene with a high base editing frequency. In some embodiments of the method, the high base editing frequency is defined as the base editor modifying the endogenous copy of the essential gene in at least 20% of the organisms carrying the vector and the endogenous copy of the essential gene in each generation.

ADDITIONAL EMBODIMENTS

In some embodiments of a two locus ClvR wherein the Rescue, Cargo and gRNAs are located on the third chromosome, Cas9 is located on the second chromosome, and the locus being targeted by Cas9 and gRNAs for cleavage is the tko locus, located on the X chromosome (Example 40; FIG. 20D; FIGS. 35A-35F).

In some embodiments, the construct for the “Cleaver” element comprises Cas9 under the control of nanos regulatory elements (promoter and UTRs), a 3×P3-td-tomato dominant marker gene, and an attB site to facilitate site-specific integration into the fly genome. This construct along with a phiC31 integrase helper plasmid can be injected into a fly stock that has an attP site at 59D3 on chromosome 2. Successful integration of Cas9 into the second chromosome can be identified by the expression of tdTomato in the eyes of the flies (Example 40).

In some embodiments, the “Rescue” element of two-locus ClvR (Cargo, Rescue and gRNAs) can be created by modifying the single-locus version of ClvR^(tko) from Oberhofer et al., 2019. This can be achieved by injecting Cas9/gRNA RNP-complexes into ClvR^(tko) flies. The Cas9/gRNA RNP-complexes targeted the Cas9 reading frame of ClvR^(tko) to create mutations within and abolish Cas9 function at that site. Flies carrying both the second and third chromosome constructs can be made doubly homozygous and kept as a stock (Example 40; FIG. 49A).

In some embodiments of gene drive experiments (Example 40), males homozygous for the second and third chromosome constructs can be mated with wildtype females (Example 40). At the same time wildtype males can be mated with wildtype females. Mated females at a ratio of 2:1 (mated with transgenic: mated with wildtype) can be then introduced into four bottles and allowed to lay eggs for several days. Adults can be then removed and progeny allowed to develop to adulthood. After three days of mating among this adult population, adults can be scored for the presence or absence of markers that identify the transgene-bearing third chromosome and the transgene-bearing second chromosome, using a fluorescence microscope. Adults can be then transferred to fresh bottles for three days, removed and the process repeated for a number of generations.

In some embodiments, counts of the proportion of individuals carrying the two transgenic components (Cas9 and/or Rescue+Cargo) can be plotted for each generation. A subset of the different transgene-bearing and non-transgene-bearing genotypes can be observed over time. In some embodiments, the frequency of Rescue+Cargo+gRNA-bearing genotypes increases over time, while the frequency of Cas9-bearing genotypes decreases. Whenever Cas9 and Rescue+Cargo+gRNA are found in the same individual, cleavage at the tko locus occurs. Progeny that inherit the Rescue+Cargo+gRNAs always survive because they carry at least one copy of the Rescue transgene. Individuals that inherit Cas9 but not the Rescue transgene may die if the transgene is in an individual that lack a functional copy of tko, resulting in a decrease in Cas9 frequency in the population over the generations.

In some embodiments, linkage is important in terms of thinking about the ability of ClvR to spread beyond a target area. In some embodiments, by titrating the degree of linkage between the two locus components one can titrate the extent of ClvR spread in space. In some embodiments, this can be appreciated by considering first the case of completely linked loci, single locus ClvR. In this case drive is always present. However, in some embodiments, when different degrees of linkage are present the two components of the system dissociate from each other specific kinetics. The important point is that regardless of the degree of linkage, as two locus ClvR spreads in space, drive will decrease as Cas9 segregates away from the Rescue-bearing components. In some embodiments, it will segregate slowly when recombination distances are low (e.g., 12.5 m.u.), and more rapidly when recombination distances are higher. In any case other than complete linkage, in some embodiments, segregation of Cas9 from Rescue-bearing constructs will ultimately result in loss of drive. In this way, in some embodiments, any degree of linkage makes two locus ClvR ultimately a self-limiting drive system with respect to spread in space. In some embodiments, two locus Clvr can spread to genotype fixation in a constrained area in which all the wildtype copies of the essential gene have been lost (genetic addiction) (as in FIG. 50, 12.5% recombination). But, in some embodiments, when spread in space is not constrained, the ultimate loss of Cas9 through segregation and loss in dead individuals who lack functional copies of the essential gene results in loss of drive potential.

TABLE 0.1 SEQ ID Sequence description Origin/Source NO: rescue (FIG. 17)) artifiicial 44 Dm-tko (FIG. 17)) drosophila and artificial 45 PAM (FIG. 19) artificial 46 gRNA1 (FIG. 19) artificial 47 reference (FIG. 19) wildtype sequence database 48 w[1118] control (FIG. 19) widltype sequence for this 49 strain ♂X/Y;;ClvR^(tko) offspring from mutant sequence after cleavage 50 ♀ClvRtko/+ XX ♂w[1118] mutant sequence after cleavage 51 mutant sequence after cleavage 52 mutant sequence after cleavage 53 mutant sequence after cleavage 54 mutant sequence after cleavage 55 mutant sequence after cleavage 56 mutant sequence after cleavage 57 mutant sequence after cleavage 58 mutant sequence after cleavage 59 mutant sequence after cleavage 60 mutant sequence after cleavage 61 mutant sequence after cleavage 62 mutant sequence after cleavage 63 mutant sequence after cleavage 64 mutant sequence after cleavage 65 mutant sequence after cleavage 66 mutant sequence after cleavage 67 Dvir-Tko-aa (FIG. 37) virilis tko sequence 68 Dm-Tko-aa-C (FIG. 37) melanog aster tko sequence 69 variant Dm-Tko-aa-B (FIG. 37) melanog aster tko seuqence 70 variant FIG. 39D mutant sequences in tko after 71 cleavage FIG. 39D mutant sequences in tko after 72 cleavage escF1 (FIG. 39D) mutant sequences in tko after 73 cleavage escM1A (FIG. 39D) mutant sequences in tko after 74 cleavage escM1B (FIG. 39D) mutant sequences in tko after 75 cleavage escM2A (FIG. 39D) mutant sequences in tko after 76 cleavage escM2B (FIG. 39D) mutant sequences in tko after 77 cleavage escM3A (FIG. 39D) mutant sequences in tko after 78 cleavage escM3B (FIG. 39D) mutant sequences in tko after 79 cleavage escM4A (FIG. 39D) mutant sequences in tko after 80 cleavage escM4B (FIG. 39D) mutant sequences in tko after 81 cleavage escM5A (FIG. 39D) mutant sequences in tko after 82 cleavage escM5B (FIG. 39D) mutant sequences in tko after 83 cleavage escM6A (FIG. 39D) mutant sequences in tko after 84 cleavage escM6B (FIG. 39D) mutant sequences in tko after 85 cleavage escM7A (FIG. 39D) mutant sequences in tko after 86 cleavage escM7B (FIG. 39D) mutant sequences in tko after 87 cleavage escM8A (FIG. 39D) mutant sequences in tko after 88 cleavage escM8B (FIG. 39D) mutant sequences in tko after 89 cleavage FIG. 39E mutant sequences in tko after 90 cleavage FIG. 39E mutant sequences in tko after 91 cleavage escF1 (FIG. 39E) mutant sequences in tko after 92 cleavage escM1A (FIG. 39E) mutant sequences in tko after 93 cleavage escM1B (FIG. 39E) mutant sequences in tko after 94 cleavage escM2A (FIG. 39E) mutant sequences in tko after 95 cleavage escM2B (FIG. 39E) mutant sequences in tko after 96 cleavage escM3A (FIG. 39E) mutant sequences in tko after 97 cleavage escM3B (FIG. 39E) mutant sequences in tko after 98 cleavage escM4A (FIG. 39E) mutant sequences in tko after 99 cleavage escM4B (FIG. 39E) mutant sequences in tko after 100 cleavage escM5A (FIG. 39E) mutant sequences in tko after 101 cleavage escM5B (FIG. 39E) mutant sequences in tko after 102 cleavage escM6A (FIG. 39E) mutant sequences in tko after 103 cleavage escM6B (FIG. 39E) mutant sequences in tko after 104 cleavage escM7A (FIG. 39E) mutant sequences in tko after 105 cleavage escM7B (FIG. 39E) mutant sequences in tko after 106 cleavage escM8A (FIG. 39E) mutant sequences in tko after 107 cleavage escM8B (FIG. 39E) mutant sequences in tko after 108 cleavage FIG. 40A mutant sequences in tko after 109 cleavage FIG. 40A mutant sequences in tko after 110 cleavage tko1A (FIG. 40A) mutant sequences in tko after 111 cleavage tko1B (FIG. 40A) mutant sequences in tko after 112 cleavage tko2A (FIG. 40A) mutant sequences in tko after 113 cleavage tko2B (FIG. 40A) mutant sequences in tko after 114 cleavage tko3A (FIG. 40A) mutant sequences in tko after 115 cleavage tko3B (FIG. 40A) mutant sequences in tko after 116 cleavage tko4A (FIG. 40A) mutant sequences in tko after 117 cleavage tko4B (FIG. 40A) mutant sequences in tko after 118 cleavage tko5A (FIG. 40A) mutant sequences in tko after 119 cleavage tko5B (FIG. 40A) mutant sequences in tko after 120 cleavage tko6A (FIG. 40A) mutant sequences in tko after 121 cleavage tko6B (FIG. 40A) mutant sequences in tko after 122 cleavage tko7A (FIG. 40A) mutant sequences in tko after 123 cleavage tko7B (FIG. 40A) mutant sequences in tko after 124 cleavage tko8A (FIG. 40A) mutant sequences in tko after 125 cleavage tko8B (FIG. 40A) mutant sequences in tko after 126 cleavage tko9A (FIG. 40A) mutant sequences in tko after 127 cleavage tko9B (FIG. 40A) mutant sequences in tko after 128 cleavage FIG. 40B mutant sequences in tko after 129 cleavage FIG. 40B mutant sequences in tko after 130 cleavage tko1A (FIG. 40B) mutant sequences in tko after 131 cleavage tko1B (FIG. 40B) mutant sequences in tko after 132 cleavage tko2A (FIG. 40B) mutant sequences in tko after 133 cleavage tko2B (FIG. 40B) mutant sequences in tko after 134 cleavage tko3A (FIG. 40B) mutant sequences in tko after 135 cleavage tko3B (FIG. 40B) mutant sequences in tko after 136 cleavage tko4A (FIG. 40B) mutant sequences in tko after 137 cleavage tko4B (FIG. 40B) mutant sequences in tko after 138 cleavage tko5A (FIG. 40B) mutant sequences in tko after 139 cleavage tko5B (FIG. 40B) mutant sequences in tko after 140 cleavage tko6A (FIG. 40B) mutant sequences in tko after 141 cleavage tko6B (FIG. 40B) mutant sequences in tko after 142 cleavage tko7A (FIG. 40B) mutant sequences in tko after 143 cleavage tko7B (FIG. 40B) mutant sequences in tko after 144 cleavage tko8A (FIG. 40B) mutant sequences in tko after 145 cleavage tko8B (FIG. 40B) mutant sequences in tko after 146 cleavage tko9A (FIG. 40B) mutant sequences in tko after 147 cleavage tko9B (FIG. 40B) mutant sequences in tko after 148 cleavage FIG. 40C mutant sequences in tko after 149 cleavage FIG. 40C mutant sequences in tko after 150 cleavage tkoG3-1 (FIG. 40C) mutant sequences in tko after 151 cleavage tkoG3-2 (FIG. 40C) mutant sequences in tko after 152 cleavage tkoG3-3 (FIG. 40C) mutant sequences in tko after 153 cleavage tkoG3-4 (FIG. 40C) mutant sequences in tko after 154 cleavage tkoG3-5 (FIG. 40C) mutant sequences in tko after 155 cleavage tkoG3-6 (FIG. 40C) mutant sequences in tko after 156 cleavage tkoG3-7 (FIG. 40C) mutant sequences in tko after 157 cleavage tkoG3-8 (FIG. 40C) mutant sequences in tko after 158 cleavage tkoG3-9 (FIG. 40C) mutant sequences in tko after 159 cleavage tkoG3-10 (FIG. 40C) mutant sequences in tko after 160 cleavage tkoG3-11 (FIG. 40C) mutant sequences in tko after 161 cleavage tkoG3-12 (FIG. 40C) mutant sequences in tko after 162 cleavage FIG. 40D mutant sequences in tko after 163 cleavage FIG. 40D mutant sequences in tko after 164 cleavage tkoG3-1 (FIG. 40D) mutant sequences in tko after 165 cleavage tkoG3-2 (FIG. 40D) mutant sequences in tko after 166 cleavage tkoG3-3 (FIG. 40D) mutant sequences in tko after 167 cleavage tkoG3-4 (FIG. 40D) mutant sequences in tko after 168 cleavage tkoG3-5 (FIG. 40D) mutant sequences in tko after 169 cleavage tkoG3-6 (FIG. 40D) mutant sequences in tko after 170 cleavage tkoG3-7 (FIG. 40D) mutant sequences in tko after 171 cleavage tkoG3-8 (FIG. 40D) mutant sequences in tko after 172 cleavage tkoG3-9 (FIG. 40D) mutant sequences in tko after 173 cleavage tkoG3-10 (FIG. 40D) mutant sequences in tko after 174 cleavage tkoG3-11 (FIG. 40D) mutant sequences in tko after 175 cleavage tkoG3-12 (FIG. 40D) mutant sequences in tko after 176 cleavage dribblev2 s2 (FIG. 44) artificial sequence 177 dribblev2 s2 (FIG. 44) articifial sequence 178 template sequence dribble-Dmel D. melanogaster sequence 179 (FB) (FIG. 45) Aligned sequence dribble-Dsuz D. suzukii sequence 180 (swFB BLASTN of Dmel dribble) (FIG. 45) template sequence aNeiihbornbh D. melanog aster sequence 181 5'U (FIG. 45) aligned sequence D. suzukii sequence 182 aNeiihborTRd1 TD5'1'm(FB)lsulrnbhlaNeiihbU (FIG. 45) tf2a-step2 (FIG. 47) artificial sequence 183 tf2a-step2 (FIG. 47) artificial sequence 184 tko-step2 (FIG. 48) artificial sequence 185 tko-step2 (FIG. 48) artificial sequence 186 template sequence tfIIA-D D. melanogaster sequence 187 genomic (FIG. 46) template sequence D-suzukii D. suzukii sequence 188 rescue (FIG. 46)

EXAMPLES

Outlined in Examples 1-5 are the designs of five proposed single locus cleavage mediated gene drives. Discrete generation, deterministic population frequency models were developed for each of the five drive mechanisms that demonstrate the range of fitness costs and Cas9 cleavage efficiencies for which they will take over a wildtype population.

Example 1—X Chromosome Cleavage Mediated Y Chromosome Drive

X chromosome cleavage mediated Y chromosome Drive (also referred to herein as X cleavage mediated Y drive) consists of Cas9, gRNAs which target an essential (i.e. recessive lethal) gene on the X chromosome, and a recoded copy of this target X gene which is immune to gRNA targeting, which are situated together at the same locus on the Y chromosome (FIG. 1A). The transgenic construct (TY) is situated on the Y chromosome and consists of Cas9 (long rectangle), gRNAs (short rectangle) targeting an essential gene on the X chromosome, and a recoded version of the target gene (light rectangle with recoded gRNA target sites indicated as darker squares) (FIG. 1A). Potential cleavage sites on the target essential gene (X) are indicated by dashed lines and scissors, and the cleaved locus (C) is a null form of the target gene made of what remains of the gene from the outer ends of the cleavage sites (FIG. 1A).

In males who carry this construct (TY) and a normal X chromosome (X), the target gene is cleaved multiple times during spermatogenesis, destroying the wild type copy of the gene on the X chromosome (C) and resulting in either TY or C bearing sperm (FIG. 1B). In transgenic males that bear wild type X chromosomes, Cas9 and Rescue (dark square and and light square with thin dark lines[representing recoding to gRNA resistance], respectively) can find and cleave a copy of the target gene (light square). The resulting cleaved locus (light thin bar) is passed on instead of the original target wildtype locus. When two individuals bearing a cleaved locus mate and the cleaved X loci are paired together (CC) or when the cleaved locus is passed on to a male (CY), the resulting offspring is unviable, removing wild type alleles are from the population (FIG. 1B) As TY males mate with wild type females, C's will begin to accumulate in heterozygotes (CX). All CY males and all CC females will die from the absence of a functional copy of the target essential X gene, leaving the viable genotypes CTY, XTY, XY, CX, and XX (FIG. 1B). Events proceed from left to right. The vector on the Y expresses a site-specific nuclease (dark square) and a rescue transgene (light square). The nuclease has the ability to cleave a wildtype version of the essential gene on the X at multiple positions (scissors). Cleavage does not necessarily happen in somatic cells. The left-most panel (X,Ty) simply indicates where cleavage occurs. Cleavage occurs in germline cells (CTy), resulting in the creation of an X chromosome that lacks a functional copy of the essential gene (thin light line). When a male carrying these chromosomes mates with a wildtype female new opportunities for cleavage of a wildtype X are created (second line). In the third generation matings are shown that result in the death of several genotypes.

The discrete generation, deterministic population frequency model for this drive mechanism demonstrates that if Cas9 cleaves the target gene with 100% efficiency, TY can drive to fixation amongst Y chromosomes with just a few moderate releases of CTY males while bearing a fitness cost of up to approximately 45% (FIG. 1C). TY can still drive male replacement when Cas9 is cleaving at non-optimal rates, but it can only tolerate correspondingly reduced fitness costs as a result (FIG. 1C). Discrete generation, deterministic population frequency modeling of X cleavage mediated Y drive is shown in FIG. 1C. Each data point uses a few moderate releases of transgenic mosquitoes (three releases of CTY males at 50% of the population) with the specified fitness cost and Cas9 cleavage efficiency. The shade of each data point indicates the number of generations (as indicated by the bar on the right) before TY bearing individuals make up >99% of all males. White indicates the inability of TY to take over under the specified conditions or failure to do so within 70 generations (FIG. 1C).

The X CM Y drive is capable of quickly driving a transgene to fixation on the Y chromosome while bearing ˜40% fitness costs at high cleavage efficiency. As males are the only transgenics, it cannot be used as a replacement mechanism for attacking mosquitoes because only the females are vectors. However, it can still be useful in the context of suppression if the cargo is a lethal gene under an environmentally triggered promoter. In this way, the transgene can spread to fixation in males, killing all males once the environmental trigger activates and resulting in a population crash. Alternatively, this construct can be used in ZW species where the female is the heterogametic sex, such as the pink bollworm.

Example 2—Cleavage Mediated X Drive

Cleavage mediated X drive consists of Cas9, gRNAs which target an essential gene on the X chromosome, and a recoded or sequence unrelated copy of this target X gene which is immune to gRNA targeting, which are situated together at the same locus as the target gene (FIG. 2A). Figure component labeling is as in Example 1. The transgenic construct (TX) is situated on the X chromosome and consists of Cas9, gRNAs targeting an essential gene on the X chromosome (at the same locus as TX), and a recoded version of the target gene (FIG. 2A). Potential cleavage sites on the target essential gene (X) are indicated by dashed lines and scissors, and the cleaved locus (C) is a null form of the target gene made of what remains of the gene from the outer ends of the cleavage sites (FIG. 2A).

In females who carry this construct (TX) and a normal X chromosome (X), the target gene is cleaved multiple times during oogenesis, destroying the wild type copy of the gene on the X chromosome (C) and resulting in either TX or C bearing eggs (FIG. 2B). In transgenic females that bear wild type X chromosomes (TX X) Cas9 can find and cleave a copy of the target gene. The resulting cleaved locus is passed on instead of the original target wildtype locus. When the cleaved locus is passed on to a male (CY), the resulting offspring is unviable, removing a wild type allele are from the population (FIG. 2B). As transgenic individuals mate with wild types, cleaved copies of the essential X gene will begin to accumulate in females (CX). All males that receive a cleaved X chromosome (CY) will die from the absence of a functional copy of the target essential X, leaving the viable genotypes TXY, XY, TXTX, TXC, TXX, CX, and XX (FIG. 2B).

The discrete generation, deterministic population frequency model for this drive mechanism demonstrates that if Cas9 cleaves the target gene with 100% efficiency, TX can drive to fixation with just a few moderate releases of TXY males while bearing a fitness cost of up to approximately 35% (FIG. 2C). TX can still drive population replacement when Cas9 is cleaving at non-optimal rates, but it can only tolerate correspondingly reduced fitness costs as a result (FIG. 2C). Discrete generation, deterministic population frequency modeling of cleavage mediated X drive is shown in FIG. 2C. Each data point uses a few moderate releases of transgenic mosquitoes (three releases of TXY males at 50% of the population) with the specified fitness cost and Cas9 cleavage efficiency. The shade of each data point indicates the number of generations (as indicated by the bar on the right) before TX bearing individuals make up >99% of the population. White indicates the inability of TX to take over under the specified conditions or failure to do so within 70 generations (FIG. 2C).

The X drive can tolerate ˜35% fitness costs at high cleavage efficiency. This drive is well suited to replacement in XY species of mosquitoes such as Anopheles gambiae.

Example 3—Autosomal Cleavage Mediated Autosomal Drive

Cleavage mediated autosomal drive consists of Cas9, gRNAs which target an essential autosomal gene, and a recoded or sequence unrelated copy of this target gene which is immune to gRNA targeting, which are situated together at the same locus as the target gene (FIG. 3A). The transgenic construct (T) is situated on an autosome and consists of Cas9, gRNAs targeting an essential gene (at the same autosomal locus as T), and a recoded version of the target gene (FIG. 3A). Potential cleavage sites on the target essential gene (A) are indicated by dashed lines and scissors, and the cleaved locus (C) is a null form of the target gene made of what remains of the gene from the outer ends of the cleavage sites (FIG. 3A).

In males and females who carry the construct (T) and a wild type copy of the its target (A), the target gene is cleaved multiple times during gametogenesis, destroying the wild type copy of the gene (C) and resulting in either T or C bearing gametes (FIG. 3B). As transgenic individuals mate with wild types, cleaved copies of the essential gene will begin to accumulate in heterozygotes (CA individuals). All individuals that receive two cleaved autosomes (CC) will die from the absence of a functional copy of the target essential autosomal gene, leaving the viable genotypes TT, TC, TA, CA, and AA (FIG. 3B). In heterozygotes (TA) Cas9 can find and cleave a copy of the target gene. The resulting cleaved locus is passed on instead of the original target wildtype locus. When two individuals bearing cleaved locus mate and the cleaved loci are paired together (CC), the resulting offspring is unviable, removing two wild type alleles are from the population (FIG. 3B).

The discrete generation, deterministic population frequency model for this drive mechanism demonstrates that if Cas9 cleaves the target gene with 100% efficiency, T can drive to fixation with just a few moderate releases of TT males while bearing a fitness cost of up to approximately 55% (FIG. 3C). T can still drive population replacement when Cas9 is cleaving at non-optimal rates, but it can only tolerate correspondingly reduced fitness costs as a result (FIG. 3C). Discrete generation, deterministic population frequency modeling of cleavage mediated autosomal drive is shown in FIG. 3C. Each data point uses a few moderate releases of transgenic mosquitoes (three releases of TT males at 50% of the population) with the specified fitness cost and Cas9 cleavage efficiency. The shade of each data point indicates the number of generations (as indicated by the bar on the right) before T bearing individuals make up >99% of the population. White indicates the inability of T to take over under the specified conditions or failure to do so within 70 generations (FIG. 3C).

The autosomal drive is very potent, capable of driving even with ˜55% fitness costs at high cleavage efficiency. Because the construct is autosomal, it can be used to drive replacement in any species, importantly covering both Anopheles gambiae and Aedes aegypti. It is also perhaps the easiest to implement, as the only knowledge it requires about the target species are an essential gene on an autosome and an appropriate promoter to drive expression of the DNA sequence modifying enzyme (either pre-meiotic or gametogenic).

Example 4—Cleavage Mediated 2-Locus Autosomal Drive

Cleavage mediated 2-locus autosomal drive consists of Cas9, gRNAs which target an essential autosomal gene, and a recoded or sequence unrelated copy of this target gene which is immune to gRNA targeting, which are situated together on a different autosome (wild type W) than the target gene (FIG. 4A). The transgenic construct (T) is situated on an autosome and consists of Cas9, gRNAs targeting an essential gene (at a different autosomal locus than T), and a recoded version of the target gene. The transgenic construct T is generated by targeted insertion at a wild type locus indicated by the rectangle (W). Potential cleavage sites on the target essential gene (A) are indicated by dashed lines and scissors, and the cleaved locus (C) is a null form of the target gene made of what remains of the gene from the outer ends of the cleavage sites (FIG. 4A).

In males and females who carry at least one copy of the construct (T) and at least one copy of the wild type target (A), the target gene is cleaved multiple times during gametogenesis, destroying the wild type copy of the gene (C) and resulting in C bearing gametes (FIG. 4B). As transgenic individuals mate with wild types, cleaved copies of the essential gene will begin to accumulate in heterozygotes (—CA individuals). Only individuals who do not bear a T and receive two cleaved genes (WWCC) will die from the absence of a functional copy of the target essential autosomal gene, leaving the viable genotypes TTCC, TTCA, TTAA, TWCC, TWCA, TWAA, WWCA, and WWAA (FIG. 4B). In individuals which possess at least one T and at least one A, Cas9 can find and cleave a copy of the target gene. The resulting cleaved locus is passed on instead of the original target wildtype locus. When two individuals bearing the cleaved locus mate and the cleaved loci are paired together in the absence of the transgene (WWCC), the resulting offspring is unviable, removing two wild type alleles are from the population (FIG. 4B).

The discrete generation, deterministic population frequency model for this drive mechanism demonstrates that if Cas9 cleaves the target gene with 100% efficiency, this drive mechanism is identical to the single locus cleavage based autosomal drive mechanism. However, if Cas9 cleavage efficiency is imperfect, then this 2-locus cleavage based drive can tolerate larger fitness costs than the single locus version (FIG. 4C, as compared to FIG. 3C). Discrete generation, deterministic population frequency modeling of cleavage mediated 2-locus autosomal drive is shown in FIG. 4C. Each data point uses a few moderate releases of transgenic mosquitoes (three releases of TTCC males at 50% of the population) with the specified fitness cost and Cas9 cleavage efficiency. The shade of each data point indicates the number of generations (as indicated by the bar on the right) before T bearing individuals make up >99% of the population. White indicates the inability of T to take over under the specified conditions or failure to do so within 70 generations (FIG. 4C).

The dynamics of the 2-locus autosomal drive makes it identical to the autosomal drive when the cleavage efficiency of Cas9 is perfect, but when that cleavage efficiency is reduced 2-locus drive becomes the stronger drive. As a result, it can maintain higher fitness costs at reduced cleavage efficiencies while sharing the same applicability to species and ease of creation as with single locus versions.

Example 5—Cleavage Mediated Haplolethal Drive

Cleavage mediated haplolethal drive is slightly different from the other four cleavage based mechanisms. It consists of Cas9, gRNAs which target an autosomal haplolethal gene (instead of a recessive lethal gene), and a recoded or sequence unrelated copy of this haplolethal target gene which is immune to gRNA targeting, which are situated together at the same locus as the target gene (FIG. 5A). The transgenic construct (T) is situated on an autosome and consists of Cas9, gRNAs targeting a haplolethal gene (at the same autosomal locus as T), and a recoded version of the target gene. Potential cleavage sites on the target haplolethal gene are indicated by dashed lines and scissors, and the cleaved locus is a null form of the target gene made of what remains of the gene from the outer ends of the cleavage sites (FIG. 5A).

Cleavage is male specific, so in males who carry the construct (T) and a wild type copy of its target (H), the target gene is cleaved multiple times during spermatogenesis, destroying the wild type copy of the gene (C) and resulting in either T or C bearing sperm (FIG. 5B). As transgenic males mate, cleaved copies of the haplolethal gene will immediately result in the death of their carrier (both TC and CH genotypes), leaving the viable genotypes TT, TH, and HH (FIG. 5B). In heterozygotes (TH) Cas9 can find and cleave a copy of the target essential gene. The resulting cleaved locus is passed on instead of the original wildtype locus, and any offspring that receives the cleaved locus is unviable, removing either a transgene and a cleaved locus (TC) or two wild type alleles (CH) from the population (FIG. 5B). Related constructs can be implemented, as described above for the two-locus autosomal situation, in which the construct is located at a position different from that of the gene being targeted.

The discrete generation, deterministic population frequency model for this drive mechanism demonstrates that if Cas9 cleaves the target gene with 100% efficiency, T can drive to fixation with just a few moderate releases of TT males while bearing a fitness cost of up to approximately 60% (FIG. 5C). T can still drive population replacement when Cas9 is cleaving at non-optimal rates, but it can only tolerate correspondingly reduced fitness costs as a result (FIG. 5C). Discrete generation, deterministic population frequency modeling of cleavage mediated haplolethal drive is shown in FIG. 5C. Each data point uses a few moderate releases of transgenic mosquitoes (three releases of TT males at 50% of the population) with the specified fitness cost and Cas9 cleavage efficiency. The shade of each data point indicates the number of generations (as indicated by the bar on the right) before T bearing individuals make up >99% of the population. White indicates the inability of T to take over under the specified conditions or failure to do so within 70 generations.

The haplolethal drive is even stronger than the autosomal drive, capable of driving even with ˜60% fitness costs at high cleavage efficiency. However, at reduced cleavage efficiency it withstands a smaller range of fitness costs than the 2-locus drive. Additionally, haplolethal drives rely on identifying a haploethal locus on which to base this drive mechanism as well as a pre-meiotic promoter to drive expression of either Cas9 and a post-meiotic promoter for the gRNAs, with one or both promoters also driving male specific expression. The latter two requirements are necessary for getting cleavage of the haplolethal locus in sperm without causing cleavage in the rest of the individual, thereby resulting in death of the construct-bearing individual. In some implementations Cas9 expression is limited to stages of spermatogenesis after those that require activity of the gene being targeted.

A second example of single locus ClvR targeting genes with some degree of haploinsufficiency or haplolethality is presented in FIG. 5D-G, which also illustrates the behavior of a haplosufficient locus as a point of comparison. Population genetic behavior of ClvR when targeting a haplosufficient (D, E) or haploinsufficient (F, G) essential gene. (D, E) A discrete generation, deterministic population frequency model of ClvR spread (cleavage in male and female germline; ClvR located on an autosome and the essential gene on the X; see data in Example 17) through a single panmictic population, for varying initial release ratios and fitness costs, without (D), or with (E) maternal carryover-dependent cleavage. The heatmap indicates the number of generations required for the ClvR-bearing genotype to approach fixation (i.e., >99% of the total population). (F) Heatmap showing the number of generations required for the ClvR-bearing genotype to reach fixation (<99% ClvR-bearing) for different initial release ratios and haploinsufficient fitness costs (100%=haplolethal), for a two locus autosomal version of ClvR with maternal carryover. (G) Individuals traces showing the fate of a ClvR from (F) targeting a haplolethal gene, for different release ratios. The horizontal line represents an approximation of the unstable equilibrium frequency (˜31.5%; population frequencies do not change significantly over 20 generations). Population frequencies greater than equilibrium=36%, 41%, and 46%; those below=26%, 21%, and 16%. Note that the term “Release Ratio” for all heatmaps refers to the ratio of homozygous transgenic males compared to wild type males and females after a release has occurred (e.g. a 40% release means that 40% of the population is ClvR/ClvR male, 30% is +/+ male, and 30% is +/+ female). Thus, initial release ratio also=initial population frequency. Note that for (F) and (G) ClvR itself is assumed to have no fitness cost. Such costs would further increase the minimum release ratios required for drive to occur, as in panels (D) and (E). Other examples of ClvR-mediated drive in which haploinsufficiency or haplolethality are present are found in FIGS. 31A-D.

Example 6—Maintenance of Extrachromosomal Element

FIG. 6A shows a chromosome (circle) carrying a wildtype copy of an essential gene (dark rectangle). In this example a prokaryotic chromosome carries a wildtype copy of an essential gene. FIG. 6B shows an extra-chromosomal element such as a plasmid carrying the construct (thin rectangle as nuclease and diagonal line rectangle as recoded Rescue) and any other genes (e.g., one or more cargo sequences) to be maintained in the population. An extrachromosomal element carries the vector, which carries a recoded or sequence unrelated version of the essential gene (diagonal lines) and the DNA modifying enzyme driven by a promoter (solid rectangle). FIG. 6C shows the construct, which consists of two components: (1) a site-specific DNA modifying enzyme designed to alter the sequence of an endogenous gene required for survival, proliferation, fertility, or differentiation so as to render it non-functional (left); (2) a recoded or sequence unrelated version of the essential gene resistant to cleavage, and having reduced nucleotide identity with the endogenous gene (right). Optionally, one or more cargo sequences are present (center). FIG. 6D shows the chromosome (FIG. 6A) and the extra extra-chromosomal element (FIG. 6B) in a cell and forced inheritance of the extra-chromosomal element. The endogenous copy of essential gene is altered within the cell by CleaveR to render it non-functional (FIG. 6E). However, cells that inherit CleaveR survive, proliferate, differentiate, or are fertile, whereas those that fail to inherit C fail do not survive, proliferate, differentiate, or are sterile (FIG. 6F). An expanded view of the vector shown in (FIG. 6B). Recoded essential gene (or functional equivalent that lacks significant sequence homology) transcribes to the right. DNA sequence modifying enzyme transcribes to the left. A cargo gene is located in between the two in the figure, though the actual arrangement between cargo, rescue and DNA modifying enzyme can take a number of forms. FIG. 6D shows a cell carrying the wildtype chromosome and the extrachromosomal element including the vector. FIG. 6E shows DNA modifying activity of the element results in sequence changes to the wildtype copy of essential chromosomal gene (horizontal arrow leading to a chromosome carrying a smaller version of the essential gene). FIG. 6F shows the extrachromosomal element is spontaneously lost from some cells (left). These cells die because they lack essential gene activity. Those on the right, that carry the vector and associated rescue transgene survive and proliferate.

FIG. 43 illustrates an embodiment related to Example 6 in which cells that acquire a competitor plasmid are eliminated if they end up carrying this plasmid, while losing the ClvR-bearing plasmid.

Example 7

FIG. 7 shows a schematic of an embodiment the results of a cross between organisms (in this example insects) heterozygous for the construct and a wild type organism when there is no carryover of DNA cleavage/alteration activity from germline into embryo. DNA sequence modified (parentheses) version of the essential gene is created in the female germline of heterozygotes. Both copies are cleaved, but the diploid germline cell survives because it carries one copy of the rescue transgene. Female haploid meiotic products (oocytes) survive because the essential product is provided to them from the rescue transgene. These products are inherited by progeny. All individuals inherit chromosomes carrying one sequence modified version of the essential gene. No progeny die. However, crosses between heterozygotes for the nonfunctional version of the essential gene in subsequent generations will create dead homozygotes (not shown). Note that in this example the essential locus is located on the same chromosome as the vector. This is simply for illustrative purposes as it decreases the number of genotypes that need to be shown to capture important aspects of vector behavior. As noted in the figures above, the vector can be located on any chromosome, and act to bring about sequence modifications of any essential gene, on any chromosome or extrachromosomal element. All progeny express one or both versions of the essential gene in the example provided. Therefore, all progeny survive.

Example 8

FIG. 8A shows a schematic of an embodiment of the results of a cross between heterozygous organisms when there is no carryover of DNA cleavage/alteration activity from germline into embryo. Cleavage of the essential gene occurs in the parental cell resulting in survival of progeny that express the recoded protein, and death of offspring that do no inherit CleaveR (FIG. 8A). The outcome of a cross between heterozygotes is the same whether or not there is maternal carryover. Progeny that inherit the construct survive while those that do not die. FIG. 8B shows a graph of an embodiment of CleaveR gene drive for different fitness costs and introduction frequencies without maternal transfer of DNA cleavage/alteration activity.

Example 9

FIG. 9A shows a schematic of an embodiment the results of a cross when there is maternal transfer of DNA cleavage/alteration activity from germline into embryo. Cleavage of the essential gene occurs in the parental cell and in products of cell fusion/fertilization into which the DNA cleavage/alteration activity (or the encoding RNA(s)) is introduced during oogenesis, resulting in death of offspring that do no inherit the construct (FIG. 9A). Only progeny that express the recoded protein survive. FIG. 9B shows a graph of an embodiment of gene drive for different fitness costs and introduction frequencies with maternal transfer of DNA cleavage/alteration activity.

Example 10—Meiotic Gene Drive

FIG. 10 shows a schematic of an embodiment of a meiotic gene drive. Cleavage of the essential gene occurs in the parental cell. As a result, gametes that fail to inherit CleaveR do not survive. In such a system chromosomes that carry the vector have a selective advantage and increase in frequency. Such a system can also be used to guarantee that gametes arising from a transgenic individual always carry the transgenes of interest (by virtue of tight genetic linkage to the construct). This ability has applications in agriculture, as it provides a method for regulating gene flow between populations of different genotypes.

Example 11—Sex Ratio Distortion

FIG. 11 shows a schematic of an embodiment of vector-mediated sex ratio distortion. A gene essential for post-meiotic sperm development is expressed on the Y chromosome as a part of the drive element. Only Y-bearing sperm, generated from diploids in which the drive element/vector has eliminated a gene required in haploid stages for sperm function, will express the product of this essential gene and be able to complete spermatogenesis/carry out fertilization. This results in sex-ratio distortion if sperm in which the gene has been inactivated fail to develop/undergo fertilization. Such a technology has many uses when the goal is to bring about population reduction or elimination by biasing the sex ratio towards males. A related approach can also be used to bias sex ratios towards males in species in which males are the homogametic sex (ZZ) and females the heterogametic sex (ZW). It can also be used for similar ends in species in which maleness is determined by a dominant allele of a male-determining locus. The primary requirement is that it be possible to eliminate and replace the activity of a gene required in haploid stages of sperm function, and that this product not be able to rescue meiotic brothers to which they may be linked by cytoplasmic bridges until late in spermatogenesis.

Example 12—Comparison of DNA Sequence Modification-Based Gene Drive with Homing-Based Gene Drive—1

FIG. 12 shows a schematic of an embodiment of a homing endonuclease-based cleavage of target gene for gene drive. The HEG cuts at a neutral locus in the wildtype chromosome, located at the same position in the genome as the HEG. The presence of the HEG disrupts the HEG cleavage site. In this example, the HEG carries a cargo gene located between the homology arms. In the middle panel, the HEG cleaves the wildtype allele. In the lower panel homologous recombination (HR) is used to repair the DNA break using the HEG-bearing chromosome as a template. Successful HR results in copying of the HEG into the cleaved chromosome. Cleavage of neutral locus by the homing nuclease results in the homing of gene drive and cargo genes into cleaved chromosome. This results in an increase in the population frequency of the HEG and its cargo transgene. However, homing to the neutral locus is required, which may be inefficient. Additionally, the cargo gene needs to be copied, which may not always occur, and development of resistance of neutral locus sequences to cleavage is very common. In contrast, with the DNA sequence modification-based drive method described herein (FIG. 8A, FIG. 9A), cleavage of the essential gene results in death of progeny that lack functional copies of the essential gene, i.e., both endogenous copies are cleaved and the recoded copy of the essential gene is not inherited, and results in survival of only those progeny that inherit cargo and recoded copy of the essential gene. Additionally, there is no need for the cargo to be copied as the cargo transmitted with the chromosome. Additionally, homing is not required or utilized, and occurrence of essential genes resistant to cleavage would be rare. Additionally, some species have low rate of germline HDR, greatly if not completely hindering homing based strategies.

Example 13—Comparison of DNA Sequence Modification-Based Gene Drive with Homing-Based Gene Drive—2

FIG. 13 shows a schematic of an embodiment of a homing endonuclease-based cleavage of target gene for gene drive. The HEG cleaves an essential gene. Homing occurs into the cleaved essential gene, resulting in loss of essential gene function, and an increase in the frequency of the HEG, but only under specific conditions, since loss of both copies of an essential gene results in death or infertility. The recoded essential gene and a cargo are located elsewhere in the genome. As the frequency of the HEG increases, versions of the other chromosome that carry the recoded rescue and cargo are selected for, resulting in their spread. It is important to note that homing (which requires homologous recombination) is required for this version of population replacement to work. Cleavage alone is not sufficient as it only results in loss of essential gene function, but not an increase in HEG frequency. It is only with homing (and homologous recombination) that the frequency of the HEG increases. Progeny that inherit the chromosome with recoded essential gene and cargo survive but may experience a fitness cost in an otherwise background, which would result in their loss. Only progeny that inherit two inactive copies of the essential gene die. In contrast, with the DNA sequence modification-based drive method described herein (CleaveR; FIG. 8A, FIG. 9A, FIGS. 20A-D and FIGS. 21A-C), only cleavage is required, and cleavage of the essential gene results in death of progeny that lack functional copies of the essential gene, i.e., both endogenous copies are cleaved and the recoded copy of the essential gene is not inherited, and results in survival of only those progeny that inherit cargo and recoded copy of the essential gene, which are tightly linked. The DNA sequence modification-based drive mechanism described herein does not utilize or depend on homing, only DNA sequence modification and tight linkage to a rescuing transgene.

Example 14—Comparison of DNA Sequence Modification-Based Gene Drive with Medea

FIG. 14 shows a schematic of an embodiment of a Medea-based gene drive. In Medea-based gene drive a maternally deposited toxin (which may consist of maternally expressed miRNAs that result in a loss of an essential gene, as well as a protein-based toxin, (c.f. Chen et al., 2007)) has the potential to cause the death of all embryos. However, those that inherit a tightly linked antidote survive (which may include a version of the maternally expressed gene being targeted by the maternally expressed miRNAs (c.f. Chen et al., 2007)) because they turn on expression of the antidote just in time to prevent toxin action. In this drive mechanism there is no DNA sequence modification of an endogenous locus. The mechanism of action requires that a maternal (or paternal) toxin be deposited into the embryo. In the Medea-based system, a toxin is expressed in maternal germline resulting in the toxin being present in all oocytes/eggs. Embryos that inherit Medea survive because they express an antidote in the early embryo, while those that do not inherit Medea die. In the Medea-based system, maternal expression of a toxin which can kill embryos but not oocytes is required, and rescue is achieved through early embryo expression of an antidote. In contrast, with the DNA sequence modification-based drive method described herein (CleaveR; FIG. 8A, FIG. 9A), cleavage of the essential gene results in death of progeny that lack functional copies of the essential gene, i.e., both endogenous copies are cleaved and the recoded copy of the essential gene is not inherited, and results in survival of only those progeny that inherit cargo and recoded copy of the essential gene. The DNA sequence modification-based drive mechanism described herein only requires DNA sequence modification and does not require maternal or paternal deposition of a toxin. Additionally, germline expression of a DNA modifying enzyme that targets an essential gene occurs, and rescue achieved through inheritance of a recoded version of an essential gene.

Example 15—Cleavage Mediated Drive Targeting an Essential Gene on the X-Chromosome, Proof of Concept in Drosophila melanogaster

Example 15 is an embodiment of a single locus CleaveR drive system showing reduction to practice. FIG. 15A shows a schematic of an embodiment of a Construct A with a U6:3-gRNA, an attP site, the tko rescue copy from Drosophila virilis (Dv) and a ubiquitous opie2-td-tomato marker. Only elements between the homology arms were inserted into the germline via Cas9 mediated HR. FIG. 15B shows an embodiment of a Construct B with an attB site, a 3×P3-GFP marker, Cas9 driven by nanos regulatory elements, and a set of four U6 driven gRNAs. Construct B was integrated into the attP landing site of construct A via phiC31 integrase. FIG. 15C shows an embodiment of the principle of ClvR. Females heterozygous for the ClvR construct create cleaved tko alleles in the germline. Additionally, active Cas9/gRNA complex is deposited maternally to all embryos. Offspring without the rescue copy will die.

The cleavage mediated autosomal drive described herein (referred to as single locus CleaveR) consists of Cas9, 4 gRNAs which target an essential gene on the X-chromosome, and a recoded copy of this target gene which is immune to gRNA targeting, which are situated together on a different autosome (chromosome 3) than the target gene (FIG. 15C). FIG. 17 shows an embodiment of an alignment of the target gene (Drosophila melanogaster tko [second line]—Examples 15 and 16) with the recoded rescue based on Drosophila virilis tko. FIG. 37 shows an embodiment of an alignment of amino acid sequence of D. virilis tko (Dvir-Tko-aa) and the two annotated protein isoforms from D. melanogaster (Dm-Tko-aa-B and Dm-Tko-aa-C).

In males and females who carry at least one copy of the construct and at least one copy of the wild type target, the target gene is cleaved multiple times during gametogenesis, destroying the wild type copy of the gene and resulting in gametes bearing cleaved tko alleles (FIG. 15C). As transgenic individuals mate with wild types, cleaved copies of the essential gene will begin to accumulate in heterozygotes.

Additionally, if the CleaveR drive system is inherited through the female germline, all of the offspring will inherit Cas9 and gRNASs. Only offspring that carries the rescue encoded by CleaveR will survive (FIG. 15C). FIG. 38A-FIG. 38D show another embodiment of the ClvR construct design and principle

Target Gene Selection and gRNA Design

Two versions of the ClvR constructs were constructed using tko (technical knockout) on the X chromosome as the target for the ClvR system. The tko gene encodes a mitochondrial ribosome protein (Royden, Pirrotta, and January 1987). It is a recessive lethal. Benchling software suite was used to design gRNAs targeting the exonic regions of the genes at 4 sites. gRNAs were used based on on-target activity ranking (Doench et al. 2016). In addition gRNAs were selected so as to not cut in the rescue constructs (i.e., gRNAs have a mutated PAM in the rescue construct to avoid any potential off-target cleavage therein) (see below).

Cloning of ClvR Constructs and Fly Germline Transformation

All plasmids were assembled with standard molecular cloning techniques and Gibson assembly (Gibson et al. 2009). All restriction enzymes, enzymes for Gibson Assembly mastermix and Q5 polymerase used in PCRs were from NEB. Gel extraction kits and JM109 cells for cloning from Zymo Research. The gRNA cassette and Cas9 were based on pCFD3(4)-dU6:3gRNA and pnos-Cas9-nos which were a gift from Simon Bullock (Port et al. 2014) (Addgene #49410 and #62208) and modified as described previously (Oberhofer, Ivy, and Hay 2018). Construct A (FIG. 15A) was inserted into the fly germline via Cas9 mediated homologous recombination. Construct B (FIG. 15B) was integrated into an attP landing site within construct A using the phiC31 site-specific integration system.

The experiment was started with a plasmid having a dU6:3 promoter and a modified guide scaffold (Dang et al. 2015) separated by BsmBI cutsites from previous work (Oberhofer, Ivy, and Hay 2018), which was based on pCFD3-dU6:3gRNA, a gift from Simon Bullock (Addgene plasmid #49410) (Port et al. 2014). Restriction digestion was performed with BsmBI and ligated annealed oligos (P0-68E FWD+P0-68E REV) as described on flycrispr.molbio.wisc.edu. This gRNA targets a region on the third chromosome (68E) which was chosen based on the location of an attP landing site in a widely used fly strain, zh-68E (Bischof et al. 2007). Next, the plasmid was cut with HindIII and SpeI and the following 4 fragments were assembled in a Gibson reaction (Gibson et al. 2009) to yield plasmid p68-tko-step1 (see FIG. 15A):

Two homology arms, approximately 1 kb in length up and downstream of the above gRNA target site were amplified from genomic DNA with primers P9+P10 and P15+P16; an attP site with primers P11+P12; a 4.2 kb rescue fragment with primers P13+P14. The rescue fragment was based on the tko genomic region of Drosophila virilis, a distant Drosophila species (Drosophila 12 Genomes Consortium et al. 2007). Additionally, 6 silent point mutations were introduced in the ORF of Dv-tko in order to avoid homology stretches >14 bp. The rescue was gene synthesized by IDT as two gBlock fragments with an additional 2 point mutations introduced in the intron to work around a synthesis complexity issue. Finally, a td-tomato marker (Shaner et al. 2004) driven by the ubiquitous opie2 promoter (Theilmann and Stewart 1992) with primers P15+P16 was used as the dominant marker.

Construct p68-tko-step1 (see FIG. 15A) was injected into a fly strain expressing Cas9 in the germline under nanos regulatory regions (Bloomington stock #54591) (Port et al. 2014). All injections were carried out by Rainbow Transgenic Flies.

Male injected G0 flies were outcrossed to w- and the progeny was scored for ubiquitous td-tomato expression. Male transformants were crossed to a TM3,Sb/TM6b,Tb balancer stock. Flies carrying the marker over TM3,Sb, were pooled and used as the injection strain for the 2nd construct following below.

For construct tko-step2 (FIG. 15B and FIG. 48), two constructs having two gRNAs each were subcloned. Construct pU6:3-U6:1-tandem (Oberhofer, Ivy, and Hay 2018) (based on (Port et al. 2014)) was digested with BsmBI and ligated back in two gRNAs encoded in the primer overhangs: P21+P22 and P23+P24.

A plasmid that had a 3×P3-GFP marker gene, an attB site as well as parts of nos-Cas9-nos flanked by gypsy insulators was digested with EcoRV and BglII. In a three fragment Gibson reaction full length nos-Cas9-nos, as well as the two gRNA cassettes from above were assembled to yield the final construct ptko-B. Cas9 was amplified with primers P25-nosCas9 FWD+P26-nos-Cas9 REV, guide cassette A with P27-guidesA FWD+P28-guidesA REV, and guide cassette B with P29-guidesB FWD+P30-guidesB REV.

Construct B was injected along with a phiC31 helper plasmid (Rainbow Transgenic Flies). Injected GO flies were outcrossed to w- and the progeny was screened for 3×P3-GFP expression. Transgenic males were used to cross to the balancer stock TM3,Sb/TM6b,Tb as well as w[1118]. Flies carrying the GFP marker over TM3,Sb were pooled to generate the balanced stock and flies homozygous for the ClvR construct were collected in the next generation. All primers are shown in TABLE 1, and vector sequences are provided in SEQ ID NO: 39 (p68-tko-step1; FIG. 15A), SEQ ID NO: 40 (tko-step2; FIG. 15B), and SEQ ID NO: 41 (Dvir-rescue-modified; “rescue” in FIG. 15A and FIG. 17).

TABLE 1 PRIMERS SEQ ID Primer Sequence NO: P0-68E FWD gtcgTGCACAACCAGAGACTGGAG 1 P0-68E REV aaacCTCCAGTCTCTGGTTGTGCA 2 P9-68E-hr-left FWD cttattacgtggccaactaggtgcccaaaatgtgtgtgga 3 P10-68E-hr-left REV GCTTCGGTGTGTCCGTCAGTgagaggttttgccgcgattt 4 P11-attP FWD aaatcgcggcaaaacctctcACTGACGGACACACCGAAGCC 5 P12-attP REV ccttgctgcccgcctgcagcAGTCGCGCTCGCGCGACTGA 6 P13-dv-tko FWD TCAGTCGCGCGAGCGCGACTgctgcaggcgggcagcaagg 7 P14-dv-tko REV gcagtgcaaaaaagttggtggggtcggacctcaagttgcatatgg 8 P15-68E-hr-right FWD tgcaacttgaggtccgaccccaccaacttttttgcactgc 9 P16-68E-hr-right REV gggcgaattgggtacaagctaggatgatgggatgctggaa 10 P21-tko-guidesA FWD ctattttcaatttaacgtcgctgcagcgatgccattccaGTTTCa 11 CgagctaTGTGgaaa P22-tko-guidesA REV ttcCAGCAtagctctGAAACtcgccaagggcgttgtcctgCgaagtt 12 cacccggatatct P23-tko-guidesB FWD ctattttcaatttaacgtcgcaacattgtactgtgccgcgGTTTCag 13 agctaTGCTGgaa P24-tko-guidesB REV ttcCAGCAtagctctGAAACatcgaaagtgcgtgctggtgCgaagttca 14 cccggatatct P25-nosCas9 FWD GTTGTCTATACTATAAGATCTATAGGCACGGGAT 15 AACGCT P26-nos-Cas9 REV GCAATCACAGGTGAGCAAAAAAGCTTGGATTTC 16 ACTGGAACT P27-guidesA FWD AGTTCCAGTGAAATCCAAGCttttttgctcacctgtgattgc 17 P28-guidesA REV aatcacaggtgagcaaaaaaaattaaccctcactaaaggga 18 P29-guidesB FWD ccctttagtgagggttaattttttttgctcacctgtgatt 19 P30-guidesB REV gcagcctcgagatcgatgattgccgagcacaattgtctag 20 tko-seq1 aagcgttccaagctgcacag 21 tko-seq2 cgcacatccatttccaattg 22 tko-seq3 cacacacacaggtgcgttc 23 tko-seq4 acaactagacgttggcaatcTCACACCTTCCTCTTCTTCTT 24 tko-seq5 tcagcgggattagtgtaagt 25 tko-seq6 catatgcaacttgaggtccg 26 s2-attB-rev ttcgagaccgtgacctacat 27 s2-u631-seq AGTTCCAGTGAAATCCAAGC 28 T3-seq REV gttccctttagtgagggttaatt 29 T3-seq FWD ATTAACCCTCACTAAAGGGA 30 CAS91F ATGGACAAGAAGTACTCCATTG 31 CAS91R GATCGGTATTGCCCAGAACT 32 CAS92F2 AGCGCTAGGCTGTCCAAATC 33 CAS93F GAGAAAATCCTCACATTTCGG 34 CAS94F2 AGAGTGGAAAGACAATCCTGG 35 CAS95F CTGAACGCCAAACTGATCAC 36 CAS96F TGGACGCCACACTGATTCAT 37 CAS96R TCACACCTTCCTCTTCTTCTT 38

Example 16—ClvR Effect in Females and Males

To determine the rate of germline cleavage and carryover effect in females carrying the ClvR element, heterozygous females were crossed to w[1118] males and scored the progeny for the dominant opie2-td-tomato marker of the ClvR construct. Under normal mendelian rules only half of the progeny should carry this marker. Among the 2580 progeny from these crosses all carried the opie2-td-tomato dominant marker, showing that the system works efficiently when transmitted through females (see FIG. 9A and FIG. 16A), data in the Punnett square below each cross figure.

To determine the cleavage rate in the male germline, crosses were set up between males heterozygous for the ClvR element and females carrying a mutant copy of tko over the FM7a X-chromosome balancer (tko³/FM7a/Dp(1;2;Y)w+, BDSC_4283). Female offspring of this cross will inherit one X-chromosome from the father and one from the mother. Female offspring inheriting the mutant tko allele from the mother and not carrying the ClvR element with the rescue copy of tko will be dead, if tko was cleaved in the male germline (see FIG. 16B).

For FIG. 16A, B, female is shown on the left, male is shown on the right, and Cas9/gRNA complex is indicated as scissors. Top row in Panel A and B indicates the cross, lower row shows a punnett square with gametes indicated and numbers of scored progeny in the corresponding fields. Numbers showing the effect of CleaveR are indicated (FIG. 16A) Females heterozygous for the CleaveR system were crossed to wildtype males. The Cas9/gRNA complex encoded by the CleaveR element, cleaves all wildtype copies of tko in the female germline. In addition active complexes get deposited maternally into all embryos, leading to subsequent cleavage of the paternal tko allele in the zygote. Only offspring that inherited the rescue copy from the CleaveR construct were viable, showing that the CleaveR system works efficiently in the female germline and also brings about maternal carryover-dependent cleavage. In FIG. 16B, males heterozygous for the CleaveR element were crossed to a tko mutant. The only copy of widtype tko on the single male X-chromosome was cleaved in the male germline by the CleaveR system. When the cleaved tko allele was paired with the maternal mutant X-chromosome (tko3), only those animals that also inherit the rescue encoded by the CleaveR element survived, all others died. Actual data is shown in the Punnet squares below each cross. Results showed successful implementation of the DNA sequence modification-based gene drive according to the embodiments disclosed herein. FIG. 42A-FIG. 42C show another example of the effect of ClvR effect in females and males.

Example 17—ClvR Effect in Females and Males

FIG. 18A show a schematic of an embodiment of the components of the DNA sequence modification-based gene drive implemented in the example below, targeting the X-linked locus tko in Drosophila, using a third chromosome-based gene drive element. FIG. 18B (SEQ ID NO: 42) shows a schematic of an embodiment of the components of the step 1 transgenic created for the DNA sequence modification-based gene drive implemented for targeting the X-linked locus tko in Drosophila, using a third chromosome-based gene drive element. This construct was inserted into the Drosophila genome using homologous recombination, based on the left and right homology arms. FIG. 18C (SEQ ID NO: 43) shows a schematic of an embodiment of the components of the step 2 construct created for the DNA sequence modification-based gene drive implemented for targeting the X-linked locus tko in Drosophila, using a third chromosome-based gene drive element. This construct was inserted into the step 1 genomic region using the attb site-specific integrase target site. FIG. 19 shows an embodiment Sanger sequencing results of the gRNA1 target region of the Drosophila wildtype version of the tko gene and offspring: ♂ClvR^(tko)/+ offspring from ♀ClvR^(tko)/+XX ♂w[1118] parents. The wildtype sequence is shown as well as products of ClvR action, which contain indels. Two flies were sequenced from 9 different single fly crosses each. All 18 analyzed flies showed indels of varying sizes at the gRNA1 target site. Results showed successful implementation of the DNA sequence modification-based gene drive according to the embodiments disclosed herein.

In some embodiments, any of the embodiments or arrangements in Examples 1-17 and Example 24 can be modified for a two vector or two locus arrangement, as described herein. See, Example 40 and FIG. 49A-49E for a specific implementation.

Example 18

ClvR selfish genetic elements can be implemented in single locus or two-locus formats. FIGS. 20A-D show schematics of embodiments of single locus ClvR (FIG. 20A), and two locus ClvR involving components located on two separate chromosomes (FIGS. 20B-D). In single locus ClvR the Rescue transgene and any associated cargo are always inherited together with components encoding the DNA sequence modifying enzyme. In contrast, in two locus ClvR, the ClvR components are distributed between two separate chromosomes. In this latter configuration they are free to segregate independently from each other during meiosis or other times when the two different genetic elements they are associated with are not co-inherited. Independent segregation gives two locus ClvR multiple unique characteristics: drive is transient, limited in space, and reversible. These points are detailed in Examples 34 and 35.

Example 19

In two locus ClvR with recombination, ClvR components are located on the same chromosome at some distance less than 50 map units away from each other. This configuration is illustrated for three different two locus ClvR configurations in FIGS. 21A-C. FIGS. 21A-C show schematics of embodiments of two locus ClvR involving components located on the same chromosome at a distance of less than 50 map units. Gene drive in this configuration will have behavior intermediate between that of single locus ClvR and two locus ClvR in which the components parts are freely recombining, on the same chromosome but separated by greater than 50 map units, or on separate chromosomes. Drive in such a system starts out similar to that of single locus ClvR, but begins to decay as recombination separates the components. Since this decay occurs more slowly than with two locus ClvR on separate chromosomes, drive remains stronger for a larger number of generations. However, ultimately, as with two locus ClvR on two different chromosomes, the frequency of the gene or genes encoding the DNA sequence modifying enzyme decrease as they find themselves in individuals lacking a functional copy of the essential gene. In consequence, ultimately, as with two locus ClvR in Example 18, ClvR with recombination is transient, limited in space, and reversible through dilution with wildtypes. These points are illustrated in a population genetic model for two locus ClvR on two different chromosomes in FIGS. 34A-F and FIGS. 35A-F and FIG. 50, Example 41.

Example 20

Separation of a functional Rescue from the Cargo can be prevented (or reduced) by locating the Cargo in an intron of the Rescue. Cargo and recoded rescue will often have minimal homology with surrounding sequences on homologous chromosomes, and thus are unlikely to recombine away from each other through traditional homologous recombination during meiosis. However, a break between the two genes followed by reciprocal end joining with the same region on the homologous chromosome could potentially separate them, though the frequency of this kind of event is unclear. Locating the ClvR cargo in an intron of the Rescue transgene (bottom panel) prevents breakage and end joining-mediated separation of a functional Rescue (the key component driven into the population by ClvR) from the Cargo. Separation could otherwise generate empty ClvR elements (ClvR^(Δcargo), top panel), or Rescue only elements (ClvR^(rescue), middle panel), the spread of which provide no beneficial function. Crossed lines indicate sites of chromosome breakage and end joining with a similar position on a homologous chromosome. Recombinant products of interest are indicated by the dotted lines. FIG. 22 shows a schematic of an embodiment of ClvR in which the Cargo transgene is located in an intron of the Rescue transgene. Similar considerations apply to two locus versions also.

Example 21

Separation of a functional Rescue from the Cargo can be prevented (or reduced) by locating the Cargo between two transgenes whose co-expression is required to produce a functional Rescue essential enzyme, such as dihydrofolate reducatse. In FIG. 23 the 5′ half of DHFR is driven by its own promoter. The 3′ half is driven by a strong ubiquitous promoter. The two domains are brought together to form an active enzyme through heterodimerization, mediated by specific domains at the N-terminus of each protein (boxes with diagonal lines). FIG. 23 shows a schematic of an embodiment of ClvR in which the cargo is located between two transgenes whose co-expression is required to create a functional Rescue protein. Similar considerations apply to two locus versions also.

Example 22

Separation of a functional Rescue from the Cargo can be prevented by locating the Cargo between two transgenes whose co-expression is required to produce a functional Rescue protein. Here this is achieved using a two-component transcription-based system. The gene promoter from the essential gene drives the expression of a heterologous transcriptional activator such as GAL4. The Rescue transgene contains GAL4 UAS binding sites sufficient to drive GAL4-dependent expression, upstream of an otherwise promoterless (lacking its own promoter), recoded Rescue transgene. FIG. 24 shows a schematic of an embodiment of ClvR in which the Rescue and the Cargo transgenes are arranged such that the Cargo is located between two transgenes, the presence of both of which is required for expression of a functional Rescue transgene. Similar considerations apply to two locus versions also.

Example 23

When cleavage results in a DNA break it can be repaired using multiple repair pathways, including homologous recombination. When homologous recombination is used the sequence of the repair template is important. If the repair template encodes a modified sequence that is LOF with respect to the essential gene and uncleavable (due to the sequence modification(s)), then the LOF allele is copied in place of the wildtype cleaved allele. In this way single and two locus versions of ClvR can create new LOF alleles through homologous recombination as well as through error prone pathways such as non-homologous end joining or microhomology-dependent end joining. FIG. 25 shows a schematic illustrating how ClvR can create LOF alleles using homologous recombination.

If ClvR-encoded DNA sequence modifying activity is able to move between cells in a population its relative frequency can increase as the essential gene in neighboring wildtype cells is modified to a LOF sequence. FIG. 26 shows a schematic illustrating how movement of the site-specific DNA modifying enzyme between cells can result in selection for ClvR-bearing genotypes.

Example 24

ClvR mediated drive targeting an essential gene on the second or third chromosomes, proof of concept reduction to practice in Drosophila melanogaster.

Creation of ClvR^(Tf2a). The Drosophila gene TfIIas was chosen for targeting. A rescue version, carrying many changes from that of Drosophila melanogaster (as shown in FIG. 46) was introduced into the same third chromosome site as for ClvRtko. Flies carrying this construct then had introduced into the same locus a step 2 construct encoding gRNAs designed to target Drosophila melanogaster TfIIas, but not the recoded version (as shown in FIG. 47). This construct is shown in FIG. 27.

Creation of ClvR^(dbe). The Drosophila gene dbe was chosen for targeting. A rescue version, carrying many changes from that of Drosophila melanogaster (as shown in FIG. 45) was introduced into the same third chromosome site as for ClvR^(tko). Flies carrying this construct then had introduced into the same locus a step 2 construct encoding gRNAs designed to target Drosophila melanogaster dbe, but not the recoded version (as shown in FIG. 44). This construct is shown in FIG. 28.

Drive of ClvR^(tko) in Drosophila. The frequency of ClvR-bearing individuals (ClvR/+ and ClvR/ClvR) is indicated on the y-axis and the generation number on the x-axis of FIG. 29A-FIG. 29D. Drive replicates are shown in solid lines, and predicted drive behavior (Model) is shown in dotted lines. FIG. 29A shows data for Drive 1: ♂ClvR^(tko)/+ XX ♀w¹¹¹⁸ as generation 0.

FIG. 29B shows data for Drive 2: ♂ClvR^(tko)/ClvR^(tko) XX ♀w¹¹¹⁸ and ♂w¹¹¹⁸ XX ♀w¹¹¹⁸ at a 1:1 ratio as generation 0. FIG. 29C shows data for Control drive: ♂tkoA/+ XX ♀w¹¹¹⁸ as generation 0. For the control drive flies carrying construct tkoA were used (see methods) that had only the rescue and the td-tomato marker, but no Cas9 and gRNAs. FIG. 29D shows data for allele frequency of Clvk^(tko) in drive 1. 100 males were taken from each replicate of the drive experiment after generation 7 and generation 10, outcrossed them to w¹¹¹⁸ virgins, and scored the progeny for the ClvR marker. If all progeny had the ClvR marker the male parents were considered to be homozygous. Replicates coming from drive 1 are shown. The Model curve is the predicted ratio inferred from modeling of the drive with the parameters determined from TABL2 and TABLE 3, and the assumption of no fitness cost to those carrying ClvR (See, TABLE 10 for counts).

Drive of ClvR^(tk2a) and ClvR^(dbe) into Drosophila, and comparison with ClvR^(tko). Drive plots are shown for all three ClvR elements and control drive experiments utilizing transgenics carrying only the step 1 construct, which carries the Rescue transgene, but lacks Cas9 or gRNAs. All gene drive constructs spread rapidly, while controls do not, demonstrating that ClvR-dependent gene drive works when targeting a variety of different genes. FIG. 30 shows data from Example 17 and Example 24 illustrating drive to genotype fixation in Drosophila for ClvR^(tko), ClvR^(tk2a) and ClvR^(dbe).

Example 25

For many genes loss of one copy results some fitness cost: a degree of haploinsufficiency. In extreme cases loss of one copy in a diploid can result in haplolethality, the death of heterozygotes. FIGS. 31A-D show the population genetic behavior of ClvR when targeting a haplosufficient (FIG. 31A, FIG. 31B) or haploinsufficient (FIG. 31C, FIG. 31D) essential gene (A,B) A discrete generation, deterministic population frequency model of ClvR spread (cleavage in male and female germline; ClvR located on an autosome and the essential gene on the X; see data in FIGS. 42A-C and FIGS. 29A-D) through a single panmictic population, for varying initial release ratios and fitness costs, without (FIG. 31A), or with (FIG. 31B) maternal carryover-dependent cleavage. The heatmap indicates the number of generations required for the ClvR-bearing genotype to approach fixation (i.e., >99% of the total population). (FIG. 31C) Heatmap showing the number of generations required for the ClvR-bearing genotype to reach fixation (<99% ClvR-bearing) for different initial release ratios and haploinsufficient fitness costs (100%=haplolethal), for a two locus autosomal version of ClvR with maternal carryover. (FIG. 31D) Individuals traces showing the fate of a ClvR from (FIG. 31C) targeting a haplolethal gene, for different release ratios. The horizontal line represents an approximation of the unstable equilibrium frequency (˜31.5%; population frequencies do not change significantly over 20 generations). Population frequencies greater than equilibrium=36%, 41%, and 46%; those below=26%, 21%, and 16%. Note that the term “Release Ratio” for all heatmaps refers to the ratio of homozygous transgenic males compared to wild type males and females after a release has occurred (e.g. a 40% release means that 40% of the population is CUR/ClvR male, 30% is +1+male, and 30% is +1+female). Thus, initial release ratio also, initial population frequency. Note that for (C) and (D) ClvR itself is assumed to have no fitness cost. Such costs would further increase the minimum release ratios required for drive to occur, as in panels (FIG. 31A) and (FIG. 31B). FIG. 31A-FIG. 31D show graphs of an embodiment of a population frequency modeling of cleavage mediated drive for genes that are haploinsufficient or haplolethal. See also, FIG. 41.

Example 26

A circuit that selects against mutation of Cas9/gRNAs to inactivity. While the spread of Cargo into a panmictic population is resistant to mutational inactivation of Cas9/gRNAs (A-C), the situation is likely to be more complicated in populations in which wildtype are continually migrating into the population. Once active Cas9-bearing ClvR has been eliminated in favor of elements carrying inactive Cas9 (B), the wildtype non-ClvR-bearing chromosome will spread since it lacks the fitness cost associated with presence of the cargo. To delay this outcome it is proposed that Cas9 activity can be made essential for Rescue function. A variant of Cas9 known as Cas9-VPR includes a domain that can activate transcription following DNA binding. Cas9-VPR can also bring about cleavage of full length target sites. Importantly, however, Cas9-VPR can also bind truncated gRNA target sites and drive transcription of a nearby gene, without cleaving these sites (Kiani, S. et al., 2015) In this way the exact same gRNAs and Cas9 are used for cleavage and transcriptional activation. The figure proposes that Cas9 expression is driven by the promoter of the essential gene. the gRNAs are expressed ubiquitously under U6 promoter control, as usual. Cas9 and gRNAs will cleave the wildtype copy of the essential gene in all tissues in which the essential gene is expressed. Cas9 and gRNAs will also drive expression of a promoterless, recoded version of the essential gene (the Rescue) in these same tissues. The system thus creates tight linkage between components required for cleavage and those required for rescue. It can fail due to point mutations in Cas9 that allow target site DNA binding and transcriptional activation but that prevent cleavage, as with dead Cas9 variants used for transcriptional regulation or visualization of specific genomic loci. These will happen, but are very specific mutations, and thus any spread of dead Cas9 within the population should be delayed. An important requirement for this approach is that the essential gene be expressed in the germline at levels sufficient to bring about Cas9-dependent germline cleavage of the wildtype essential gene. Also note that unless the essential gene is only required in the germline, Cas9 will be expressed and active in some somatic tissues. FIG. 32 shows a schematic illustrating a strategy by which Cas9, gRNAs and Rescue transgene can be implemented such that Cas9 and gRNAs are required for Rescue expression in addition to cleavage of an essential gene. See also, FIG. 41.

Example 27

Mutation of cargo genes or loss of effectiveness as a result of evolution of the host, or other species such as pathogens on which they are meant to act, requires strategies for removing an old element from the population and replacing it with a new one. Removal of a first generation ClvR, coupled with replacement by a second generation ClvR element. Multiple rounds of population replacement can be carried out by locating ClvR^(n+1) at the same site as ClvR^(n), with ClvR^(n+1) targeting essential gene^(n+1) while also carrying the original rescuing copy of essential gene^(n). Because progeny carrying ClvR^(n) are sensitive to loss of essential gene^(n+1), only those carrying ClvR^(n+1) survive, regardless of their status with respect to ClvR^(n). The function of ClvR^(n+1) can be made completely orthogonal to that of ClvR^(n) through the use of Cas9/gRNA variants from other species that cannot load the gRNAs generated by ClvR^(n). FIG. 33 shows schematics illustrating how second generation ClvR elements can be used to replace first generation elements when both are located at the same position in the genome.

Example 28

When ClvR components are located at two freely recombining positions in the genome, with the first locus encoding a functional DNA sequence modifying enzyme and the second locus encoding a Rescue and associated Cargo genes (two locus ClvR, version 1), gene drive is strong but transient. ClvR components are on two different chromosomes, and segregate independently at meiosis. This results in some gametes carrying the Cargo/Rescue but not Cas9/gRNA, others carrying Cas9/gRNA alone, and others carrying both transgene cassettes. The fate of these gametes in progeny (dead or alive) depends on when sequence modification occurs (in the germline alone or in somatic cells as well), and the presence or absence of the Cargo/Rescue. In short, the fates of the Cargo/Rescue and Cas9/gRNA components are dissociated because they do not always travel together through meiosis. An important implication of this behavior is that while with each two locus scenario the frequency of the Cargo/Rescue can increase in the population as compared to the non Cargo/Rescue bearing homologous chromosome (notwithstanding any limitations imposed by fitness costs associated with carrying the Cargo/Rescue cassette), the frequency of Cas9/gRNA (two locus version 1) or the Cas9/gRNA component not linked to the Cargo/Rescue (two locus version 2 and 3) will decrease over time since they sometimes find themselves in individuals who carry no functional copies of the essential gene, and are therefore dead. Since it is the presence of both Cas9 and gRNAs that leads to selection (indirectly, through the creation of LOF alleles of the essential gene) for the presence of the Cargo/Rescue, this means that in two locus ClvR the strength of drive (the ability create LOF alleles) wanes over time. Thus, two locus ClvR results in drive that is ultimately self-limiting, rather than self-sustaining, as is the case with single locus ClvR. Importantly, all the components of two locus ClvR already exist. They are exactly the same components as those used to implement ClvR^(tko) and ClvRs targeting other essential genes (dribble and tf2As). It is just that the components have been rearranged in terms of their chromosomal location. FIGS. 34A-F show graphs of an embodiment of a population frequency modeling of two locus ClvR, version 1. Two locus ClvR is introduced into the wildtype population at a fixed frequency of 40%, for illustrative purposes. Cas9/gRNAs cut in the male and female germline, and in embryos that derive from Cas9/gRNA-bearing mothers, due to maternal carryover of Cas9/gRNA. (left panel) Cargo/Rescue spreads to genotype fixation for a number of fitness costs, but fails to spread when costs are higher. Fitness costs are indicated by the darkness of the line, with zero fitness cost being darkest, and 60% fitness cost being lightest. Note that 30% introduction of wildtypes at generation 200 results in loss of Rescue from the population for all fitness costs except zero, which is unlikely to exist in the wild (middle panel) Frequency of Cas9/gRNAs over time. Note that the frequency decreases rapidly whenever there is a fitness cost. In the case of no fitness cost (lightest line) the frequency does not decrease because the Cargo/Rescue has gone to allele fixation and therefore there are no individuals lacking Rescue activity. This condition is unlikely to obtain in the real world. Introduction of wildtypes results in a decrease in the frequency of the cas9/gRNA. It does not cause elimination because there is no fitness cost associated with Cas9/gRNA. It has simply been diluted by wildtypes. (right panel) Frequency of cleaved, LOF alleles of the essential gene for the conditions described in the left panel. Note that whenever ClvR spreads the frequency of the cleaved LOF allele goes to fixation. This occurs because the continuous presence of Cas9/gRNA ensures complete cleavage. Addition of wildtypes at a frequency of 30% results in loss of the cleaved allele over time when there is a fitness cost. This is because there is no cleavage (Cas9/gRNAs have already been eliminated), and therefore no creation of new LOF alleles. In addition, because there is no drive, and therefore no selection for the presence of the Rescue, which also often carries a fitness cost. Finally, with decreasing levels of Rescue, wildtype alleles of the essential gene are more fit than LOF alleles (because they allow survival in the absence of the Rescue), and therefore spread. In sum, while two locus ClvR drive is strong, it is also transient, and therefore reversible through dilution with wildtypes.

Example 29

When ClvR components are located at two freely recombining positions in the genome, with the first locus encoding a first component of the DNA sequence modifying enzyme and the second locus encoding a Rescue, associated Cargo genes and a second component of the DNA sequence modifying enzyme (two locus ClvR, versions 2 and 3), gene drive is strong but transient. FIGS. 35A-F shows graphs of an embodiment of a population frequency modeling of two locus ClvR, versions 2 and 3, with the same parameters as detailed in Example 27. Fitness costs are indicated by the darkness of the line, with zero fitness cost being darkest, and 60% fitness cost being lightest. Example 40, FIGS. 49A-E provide examples of an implementation of two locus ClvR in Drosophila.

Example 30

Population genetic behavior of single locus ClvR for a constant introduction frequency of 40%, different fitness costs, and periodic introduction of wildtypes beginning at generation 200. ClvR spreads for some but not all fitness cost at the 40% introduction frequency. When ClvR spreads the introduction of wildtypes at a frequency of 30% causes only transient decrease in the frequency of ClvR. These points are illustrated in FIG. 36, which shows graphs of an embodiment of a population frequency model of single locus ClvR. Fitness costs are indicated by the darkness of the line, with zero fitness cost being darkest, and 60% fitness cost being lightest.

Example 31—Genetic Behavior of ClvR^(Tko)

Matings between heterozygous w¹¹¹⁸; ClvR^(tko)/+ males (where + indicates a third chromosome that does not carry ClvR^(tko)) and homozygous w¹¹¹⁸; +/+ females resulted in high levels of progeny viability to adulthood (95.2±2.0%), similar to those for the w¹¹¹⁸ strain used for transformation (95.9±2.0%). In addition, ˜50% (50.1±3.0%) of the adult progeny carried ClvR^(tko), as expected for Mendelian segregation and high ClvR^(tko) heterozygote fitness. Matings among homozygous ClvR^(tko) flies also resulted in high levels of viability to adulthood (95.1±1.7%), indicating that the presence of ClvR^(tko) components (in the likely absence of functional D. melanogaster tko, see below) does not result in obvious fitness costs. In contrast, when heterozygous w¹¹¹⁸; ClvR^(tko)/+ females were mated with homozygous w¹¹¹⁸; +/+ males, 53.6+1.3% of progeny did not reach adulthood, and all surviving adults carried ClvR^(tko). On the basis of these results it is inferred that the presence of ClvR^(tko) in mothers results in a very high frequency (>99%) of mutational inactivation of the D. melanogaster tko locus in the adult female germline and in the zygote through maternal carryover-dependent cleavage of the paternal allele. In consequence, those who fail to inherit ClvR^(tko) die, while those who inherit a single copy of ClvR^(tko) thrive. Data are shown in TABLE 2 (Flies of the indicated cross were allowed to lay eggs in a vial for 18 hours. Afterwards, eggs were counted and allowed to develop to adulthood. Eclosed adults and were scored for genotype, with ClvR-bearing flies identified by the presence of td-tomato (tom+)) and summarized in TABLE 3 (shows the average genotype frequencies (ClvR, td-tomato and w−) and eclosion rates in % with standard deviations from 10 replicates).

TABLE 2 SURVIVAL ASSAY ♂ClvR^(tko)/+ XX eclosion ♀w¹¹¹⁸ eggs tom+ tom− rate ratio 78 39 38 0.987 0.506 62 28 29 0.919 0.491 38 17 20 0.974 0.459 55 26 26 0.945 0.5 83 41 38 0.952 0.519 65 30 32 0.954 0.484 22 11 10 0.955 0.524 47 22 23 0.957 0.489 24 10 13 0.958 0.435 69 34 30 0.928 0.531 sum 543 258 259 eclosion rate(SD): 0.952 SD= 0.02 ratio: 0.499 0.501 SD= 0.03 ♀w¹¹¹⁸ XX eclosion ♂w¹¹¹⁸ eggs tom+ tom− rate 82 0 79 0.963 69 0 67 0.971 38 0 35 0.921 16 0 16 1 68 0 65 0.956 61 0 58 0.951 53 0 51 0.962 54 0 51 0.944 93 0 90 0.968 78 0 75 0.962 sum 612 0 587 hatch rate(SD): 0.959 SD= 0.02 ratio: 0 1 ♀ClvR^(tko)/+ XX ♂w¹¹¹⁸ eggs tom+ tom− 38 17 0 0.447 126 59 0 0.468 46 22 0 0.478 70 33 0 0.471 52 25 0 0.481 50 23 0 0.46 53 24 0 0.453 49 23 0 0.469 61 27 0 0.443 107 49 0 0.458 sum 545 253 0 hatch rate(SD): 0.464 SD= 0.013 ratio: 1 0 ♀ClvR^(tko)/ClvR^(tko) XX ♂ClvR^(tko)/ClvR^(tko) eggs tom+ tom− 56 53 0 0.946 64 62 0 0.969 50 47 0 0.94 73 69 0 0.945 42 39 0 0.929 45 43 0 0.956 58 56 0 0.966 51 47 0 0.922 59 56 0 0.949 87 82 0.943 sum 388 369 0 hatch rate(SD): 0.951 SD= 0.017 ratio: 1 0

TABLE 3 SUMMARY OF DATA IN TABLE 2 Cross td-tomato+ w− Eclosion rate A ♀w¹¹¹⁸ XX ♂w¹¹¹⁸  0 100 95.9 ± 2.0 B ♀w¹¹¹⁸ XX ♂ClvR^(tko)/+ 49.9 ± 3.0 0.1 ± 3.0 95.2 ± 2   C ♀ClvR^(tko)/+ XX ♂w¹¹¹⁸ 100  0 46.4 ± 1.3 D ♀ClvR^(tko) XX ♂ClvR^(tko) 100  0 95.1 ± 1.7

Example 32—Crosses to Determine Rate of D. melanogster Tko Gene Inactivation Due to Female Germline Cleavage and Maternal Carry Over-Dependent Cleavage

Shown in TABLE 4 are the offspring genotype frequencies for a cross between w¹¹¹⁸; ClvR^(tko)/+ females and w¹¹¹⁸ males. Flies were scored as ClvR-bearing based on the presence of the td-tomato marker. Of 3736 flies scored, one did not have the td-tomato marker, resulting in a cleavage rate of 0.9997. All crosses were single fly crosses if not otherwise noted (pool=a few flies; bottle=many flies (˜50)).

TABLE 4 cross tomato+ tomato− ratio note  1 61 0 1  2 50 0 1  3 63 0 1  4 62 0 1  5 49 0 1  6 48 0 1  7 50 0 1  8 127 0 1 pool  9 55 0 1 10 33 0 1 11 52 0 1 12 203 0 1 pool 13 99 0 1 pool 14 45 0 1 15 42 0 1 16 72 0 1 17 53 0 1 18 23 0 1 19 49 0 1 20 49 0 1 21 38 0 1 22 32 0 1 23 39 0 1 24 12 0 1 25 46 0 1 26 7 0 1 bottle 868 0 1 bottle 1 bottle 736 1 0.9986 bottle 2 bottle 672 0 1 bottle 3 SUM 3735 1 0.99973

Example 33—Crosses to Determine Male Germline Cleavage Rate

Shown in TABLE 5 are the offspring genotype frequencies for crosses between Clvk^(tko)/+ males and tko³/FM7a,B¹ females. Flies having the ClvR element were scored by the presence of the td-tomato marker. The tko³ mutant allele is on a w+ X chromosome; The X_(P) paternal X chromosome is w−(w¹¹¹⁸); The ClvR^(tko) element on the third chromosome is marked by the presence of td-tomato; The FM7a,B¹ Balancer X chromosome is identifiable by virtue of the Bar dominant eye marker (B¹); +refers to a wildtype third chromosome; Y refers to the Y chromosome. The male germline cleavage rate was calculated as the ratio of 8 (tko³/X_(p);;+)/907 (tko³/X_(p);;ClvR^(tko))=0.9911. The 5 escapers from bottle 2 share a common polymorphism (FIGS. 39A-E), and thus may represent multiple isolates of the same adult male germline cleavage and repair event.

TABLE 5 ♀tko³/ ♀FM7a, B¹/ ♀tko³/ ♀Fm7a, B¹/ ♂tko³/ ♂FM7a, B¹/ ♂tko³/ ♂Fm7a, B¹/ cross X_(P);;ClvR^(tko) X_(P);;ClvR^(tko) X_(P);;+ X_(P);; + Y_(P);;ClvR^(tko) Y_(P);;ClvR^(tko) Y_(p);; + Y_(P);; + 1 15 6 0 12 2 5 0 8 2 5 6 0 7 4 3 0 1 3 8 7 0 8 6 0 0 0 4 7 5 0 2 9 1 0 1 5 16 13 0 15 14 4 0 1 6 10 11 0 14 16 5 0 2 7 16 14 0 13 23 5 0 3 8 15 13 0 16 15 6 0 3 9 24 23 0 8 16 1 0 3 10 19 9 0 9 9 4 0 3 11 12 13 0 10 22 2 0 4 12 11 15 0 8 19 5 0 4 13 14 8 0 12 20 4 0 1 14 7 7 0 2 5 4 0 4 15 18 7 0 15 23 2 0 4 16 14 23 0 15 19 2 0 1 17 32 21 0 18 12 2 0 1 18 13 7 0 16 19 4 0 2 19 8 4 0 4 2 3 0 2 20 11 18 0 13 23 1 0 2 21 8 6 0 6 5 3 0 6 22 27 19 0 13 16 1 0 2 23 17 6 0 15 11 1 0 4 24 14 17 0 19 17 6 0 1 25 11 8 0 3 8 3 0 4 26 11 10 0 8 11 1 0 0 27 14 14 0 13 15 1 0 4 28 18 18 0 14 18 1 0 3 29 19 18 0 10 27 0 0 2 30 16 17 0 11 23 6 0 3 31 16 17 0 13 12 0 0 1 32 18 13 0 16 17 0 0 2 33 15 13 0 13 22 3 0 2 34 15 17 0 11 15 4 0 4 35 11 11 0 11 13 1 0 3 bottle1 219 165 3 200 216 21 0 11 bottle2 183 169 5 154 156 33 0 19 sum 907 768 8 747 880 148 0 121 total flies 3579 counted

Example 34—Analysis of Escapers

Shown in TABLE 6 are the alterations in the gRNA target sites of escaper flies. Flies are numbered based on the cross they were coming from (escF1 from bottle 2 of female Clvk^(tko)/+ mothers; escM1A-escM8B from male ClvR^(tko)/+ fathers. See, FIGS. 42A-C for mating scheme to isolate the escaper X-chromosome). ‘+’ indicates an unaltered target site, numbers indicate the size of the deletion. The last two columns show the number of progeny from an outcross of the escaper males to Clvk^(tko)/+ females, and the fraction carrying the ClvR marker td-tomato (tom+) or lacking it (tom−). The two males escM3A and esc M3B gave a mixed sequencing signal, which could not be aligned unambiguously (ND, not determined). All escapers were still sensitive to ClvR drive, as shown by the results of the outcross to ClvR^(tko)/+ females, which resulted in a progeny population in which all individuals carried ClvR^(tko) (tom+), indicating that the D. melanogaster tko locus had been disrupted in all non-ClvR^(tko)-bearing individuals.

TABLE 6 escaper g1 g2 g3 g4 tom+ tom− escF1 + + + + 62 0 escM1A 3 + + + 31 0 escM1B 3 + + + 65 0 escM2A 3 + + + 66 0 escM2B 3 + + + 62 0 escM3A ND ND ND ND 45 0 escM3B ND ND ND ND 37 0 escM4A 3 + + + 34 0 escM4B 3 + + + 48 0 escM5A 3 + + + 79 0 escM5B 3 + + + 87 0 escM6A 3 + + + 50 0 escM6B 3 + + + 68 0 escM7A 3 + + + 62 0 escM7B 3 + + + 57 0 escM8A 3 + + + 73 0 escM8B 3 + + + 85 0

Example 35—ClvR^(tko) Genotype Frequencies During Introgression into 5 Different GDL Genetic Backgrounds

Clvk^(tko)/+ females were mated each generation with GDL males. Labels of GDL lines from (35, 52) are given in the column headers. Progeny were counted and their genotypes were scored with respect to the presence of the ClvR td-tomato marker. After each generation 30 virgins were collected and backcrossed to wildtype males of the corresponding GDL stock. Shown are the numbers of scored flies with the ClvR marker td-tomato. Flies without the marker are indicated in brackets. Maternal germline and carryover-dependent mutation of the D. melanogaster tko locus was efficient since progeny lacking ClvR^(tko) were not observed, 0/7882. Data are shown in TABLE 7

TABLE 7 Generation B12 I02 N23 T01 ZW140 1 103(0) 73(0) 84(0) 90(0) 85(0) 2 184(0) 206(0) 217(0) 212(0) 194(0) 3 272(0) 221(0) 259(0) 211(0) 236(0) 4 304(0) 447(0) 316(0) 350(0) 253(0) 5 342(0) 228(0) 297(0) 206(0) 249(0) 6 540(0) 406(0) 453(0) 429(0) 415(0) SUM 1745 1581 1626 1498 1432 Total flies 7882 scored

Example 36—Sequence Polymorphisms in the Tko gRNA Target Sites Used in this Study, in Drosophila Strains from the 1000 Fly Genomes Project

Shown in TABLE 8 are pre-existing polymorphisms (SNP) in these strains, with the location and type of the SNP in the corresponding gRNA target site. The last column gives the number of gRNA target sites used in this work that are not altered in each strain. The gRNA2 target site was polymorphic in about half of the 1000 fly genomes, and was also present at some frequency in the lab strain used in the experiments, w¹¹¹⁸. With this data available it should be possible to select more conserved target sites, e.g. acagccttcagcttaacgccGGG (conserved in all), and gtgctggtgcgcctctccacCGG (SNP in one strain), though it remains to be determined if gRNAs corresponding to these sequences are highly active (see the results in the main text with gRNA3).

TABLE 8 Functional strain gRNA1 gRNA2 gRNA3 gRNA4 gRNAs US103 + G-->A (bp10) + C-->A (bp13) 2 GU6 + + + T-->C (bp10) 3 KR39 + A-->G (bp7) + C-->A (bp13) 2 RAL149 + + + C-->A (bp13) 3 RAL808 + G-->A (bp10) + C-->A (bp13) 2 SP188 + A-->G (bp7) + C-->A (bp13) 2 ZI420 + G-->A (bp10) + C-->A (bp13) 2 Z1508 + + + C-->A (bp13) 3 CO10N C-->T (bp8) + + + 3 ZI251N C-->T (bp8) G-->A (bp10) + + 2

Example 37—Molecular Analysis of ClvR Induced Mutations at the Target Locus

Shown in TABLE 9A are the type of cleavage events observed at the different gRNA target sites (g1-g4) in male progeny of Clvk^(tko)/+ mothers (from FIG. 3B). Unaltered target sites are indicated as ‘+’, polymorphisms predicted to render the target site resistant to cleavage are indicated by ‘SNP’, and gRNA target site mutations likely to result in LOF as ‘indel’. Shown in TABLE 9B, as with TABLE 9A, but with males coming from a homozygous ClvR^(tko) stock inbred for 3 generations. Note how mutations accumulate over multiple generations.

TABLES 9A & 9B TABLE 9A TABLE 9B fly g1 g2 g3 g4 fly g1 g2 g3 g4 1.1 indel + + indel 1 indel SNP + indel 1.2 indel SNP + indel 2 indel indel + indel 2.1 indel SNP + + 3 indel SNP + indel 2.2 indel SNP + + 4 indel indel + indel 3.1 indel + + + 5 indel SNP + indel 3.2 indel SNP + + 6 indel indel + indel 4.1 indel + + indel 7 indel + + indel 4.2 indel indel + indel 8 indel SNP + indel 5.1 indel indel + indel 9 indel SNP + indel 5.2 indel indel + + 10 indel SNP indel indel 6.1 indel + + + 11 indel indel + indel 6.2 indel + + + 12 indel indel + indel 7.1 indel + + + 7.2 indel + + + 8.1 indel + + indel 8.2 indel + + indel 9.1 indel + + indel 9.2 indel + + indel

Example 38—Allele Frequency of ClvR^(tko) in Drive Experiment 1. Shown are Male Outcrosses Taken from the Drive Experiment to w¹¹¹⁸ Virgins

Shown in TABLE 10 are male outcrosses taken from the drive experiment to w¹¹¹⁸ virgins. A male was considered to be homozygous if all progeny had the ClvR td-tomato marker and heterozygous if not. Note that not all of the 100 set up outcrosses produced offspring (sum of scored crosses ranged from 92-96). Data shown here was used to plot FIG. 29D.

TABLE 10 replicate generation ratio (%) sum homozygous heterozygous A 7 47.87 941 45 49 B 7 52.69 931 49 44 C 7 67.71 96 65 31 D 7 61.96 92 57 35 E 7 60.87 92 56 36 A 10 57.89 95 55 40 B 10 68.48 92 63 29 C 10 77.89 95 74 21 D 10 69.79 96 67 29 E 10 75 96 72 24 M 0 0 M 1 0 M 2 9.08 M 3 16.79 M 4 26.12 M 5 37.43 M 6 48.81 M 7 58.29 M 8 65.32 M 9 70.42 M 10 74.23 M 11 77.17

Example 39—Molecular Nature of D. melanogaster Tko Mutations Created Following Exposure to ClvR^(Tko)

To analyze the mutations in D. melanogaster tko created by ClvR^(tko), 2 ClvR^(tko)-bearing male progeny were selected from each of 9 individual single crosses (18 total flies) between heterozygous ClvR^(tko) females and w¹¹¹⁸ males (from FIG. 3B). Sequencing results from the region of the D. melanogaster tko locus spanning the gRNA-binding sites are summarized in TABLE 9A (FIGS. 40A and 40B). The gRNA1 target site contained indels of varying size in all 18 individuals. The gRNA2 target site contained a likely pre-existing polymorphism in 4 individuals (also observed in roughly half of the 1000 fly genome project strains (Lack J. B., et al., 2016)), and a 2 bp deletion in 3. The gRNA3 target site was unaltered in all individuals, and the gRNA4 target contained indels in 9 individuals. Somewhat surprisingly, larger deletions between target sites were not observed. This raises the possibility, suggested by others (Farasat, I. et al., 2016), that close juxtaposition of multiple target sites—in the present case four target sites within the 250 bp region constituting the tko open reading frame—limits Cas9's ability to simultaneously interact with and/or cleave multiple nearby target sites as a consequence of Cas9-dependent DNA supercoiling.

One implication of such a model is that mutations should accumulate at additional target sites over time, as the target sites first cleaved by Cas9 are rendered non-functional for further Cas9 binding due to mutation within the gRNA target site. To explore this possibility, and the general question of whether all gRNA target sites can be cleaved, the melanogaster tko locus was sequenced from a homozygous ClvR^(tko) stock that had been inbred for three generations (TABLE 9B; FIG. 40C and FIG. 40D). Among the twelve analyzed males, all twelve had mutations at the gRNA1 target site. The gRNA2 target site was mutated in five, unaltered in one individual, and carried the suspected common polymorphism in the remaining six. The gRNA3 target site was mutated in one fly, and the gRNA4 target site was mutated in all twelve flies. Thus, all sites can be cleaved, though cleavage efficiencies differ (from 100% for gRNA1 in generation 1 to 8% for gRNA3 after 3 generations). Many of these mutations presumably arise initially from error-prone repair by non-homologous end joining or microhomology-mediated end joining pathways. However, it is noted that ClvR may also utilize HR and homing to create new LOF alleles when the ClvR-bearing individuals introduced into the wild population carry (as the above results indicate they will) uncleavable LOF indels in the essential gene. Thus, if ClvR-bearing individuals carrying LOF indels in the essential gene mate with wildtype, ClvR-bearing progeny will be heterozygous for chromosomes that carry the LOF indels and the wildtype version of the essential gene. In the germline of these individuals, the LOF indel-bearing chromosome (which are uncleavable) could serve as a template for HR-dependent repair of cleaved wildtype alleles, converting them to the LOF sequence.

Example 40

The example presents an implementation of a two locus ClvR wherein the Rescue, Cargo and gRNAs are located on the third chromosome, Cas9 is located on the second chromosome, and the locus being targeted by Cas9 and gRNAs for cleavage is the tko locus, located on the X chromosome. This is version 3, illustrated in FIG. 20D, and as modeled in FIGS. 35A-35F.

In this example the construct for the “Cleaver” element consisted of Cas9 under the control of nanos regulatory elements (promoter and UTRs), a 3×P3-td-tomato dominant marker gene, and an attB site to facilitate site-specific integration into the fly genome. This construct along with a phiC31 integrase helper plasmid was injected into a fly stock that had an attP site at 59D3 on chromosome 2. Successful integration of Cas9 into the second chromosome was identified by the expression of tdTomato in the eyes of the flies.

The “Rescue” element of two-locus ClvR (Cargo, Rescue and gRNAs) was created by modifying the single-locus version of ClvR^(tko) from Oberhofer et al., 2019. This was achieved by injecting Cas9/gRNA RNP-complexes into ClvR^(tko) flies. The Cas9/gRNA RNP-complexes targeted the Cas9 reading frame of ClvR^(tko) to create mutations within and abolish Cas9 function at that site. Flies carrying both the second and third chromosome constructs, which are illustrated in FIG. 49A, were made doubly homozygous and kept as a stock.

In the gene drive experiment, males homozygous for the second and third chromosome constructs were mated with wildtype females. At the same time wildtype males were mated with wildtype females. Mated females at a ratio of 2:1 (mated with transgenic: mated with wildtype) were then introduced into four bottles and allowed to lay eggs for several days. Adults were then removed and progeny allowed to develop to adulthood. After three days of mating among this adult population, adults were scored for the presence or absence of markers that identify the transgene-bearing third chromosome and the transgene-bearing second chromosome, using a fluorescence microscope. Adults were then transferred to fresh bottles for three days, removed and the process repeated for a number of generations.

Counts of the proportion of individuals carrying the two transgenic components (Cas9 and/or Rescue+Cargo) were plotted for each generation for the four replicates, and are summarized in FIGS. 49B-49D. FIG. 49B and FIG. 49C present a subset of the different transgene-bearing and non-transgene-bearing genotypes observed over time, for ease of visualization. FIG. 49D presents all combinations of transgene-bearing and non-transgene-bearing genotypes. Note that the frequency of Rescue+Cargo+gRNA-bearing genotypes increases over time for all replicates, while the frequency of Cas9-bearing genotypes decreases. Whenever Cas9 and Rescue+Cargo+gRNA are found in the same individual, cleavage at the tko locus occurs. Progeny that inherit the Rescue+Cargo+gRNAs always survive because they carry at least one copy of the Rescue transgene. In contrast, those who inherit Cas9 but not the Rescue transgene may die if the transgene is in an individual that lack a functional copy of tko, resulting in a decrease in Cas9 frequency in the population over the generations.

Example 41

This example shows, using modeling, the effects of linkage between two components of the two locus ClvR system. When both components of the system are at the same locus they always travel together and have a recombination distance of 0 with respect to each other (0 m.u.=map units) (FIG. 50). In this scenario whenever the Rescue-bearing construct spreads so does Cas9. In contrast, as the distance between these two constructs increases Cas9 starts to find itself in individuals who have no functional copies of the essential gene, which results in a decrease in its population frequency over time.

An interesting case is presented by the example of a 12.5% recombination distance (m.u.=map units). As shown in FIG. 50, the frequency of the Rescue-bearing construct goes to 100%, as does the frequency of the cleaved target sequence in the essential gene. These events occur because Cas9 is found together with Rescue+Cargo+gRNAs a relatively high frequency of the time as compared with the situation in which Cas9 freely recombines with the other locus (50+% recombination). Thus, by about generation 25 all endogenous versions of the essential gene have been cleaved and the population is now dependent on (addicted to) the presence of the rescue transgene. Importantly, however, the frequency of Cas9 has decreased significantly. This means that while the population is locked into a Rescue-bearing state, its ability to engage in further drive into new space is limited, as is its ability to drive in the face of new introductions of wildtype. For any given introduction frequency the frequency of Cas9 is higher with linkage than without because Cas9 more often finds itself in Rescue-bearing individuals, and therefore survives the loss through cleavage of the endogenous copy of the essential gene. In contrast, as the distance between Cas9 and the Rescue-bearing construct increases the probability that Cas9 will find itself in individuals lacking any functional copies of the essential gene rises, resulting in its loss from the population.

For example, for the 12.5% recombination distance illustrated in FIG. 50 an implication is that while the Rescue-bearing construct has gone to 100%, the frequency of Cas9 does decrease significantly. This means that if more wildtypes were added to the population the level of drive would be decreased, as illustrated in FIGS. 34 and 35 for the case of unlinked loci, albeit more slowly. This can be useful if migration continually brings in some level of wildtype individuals. It can also be useful as a way of bringing about reversibility, through dilution with wildtypes. Linkage will often demand that more wildtypes be added than in the case of no linkage.

Linkage is also important in terms of thinking about the ability of ClvR to spread beyond a target area. In short, by titrating the degree of linkage between the two locus components one can titrate the extent of ClvR spread in space. This can be appreciated by considering first the case of completely linked loci, single locus ClvR. In this case drive is always present. However, when different degrees of linkage are present the two components of the system dissociate from each other specific kinetics. The important point is that regardless of the degree of linkage, as two locus ClvR spreads in space, drive will decrease as Cas9 segregates away from the Rescue-bearing components. It will segregate slowly when recombination distances are low (12.5 m.u.), and more rapidly when recombination distances are higher. In any case other than complete linkage, segregation of Cas9 from Rescue-bearing constructs will ultimately result in loss of drive. In this way any degree of linkage makes two locus ClvR ultimately a self-limiting drive system with respect to spread in space. Two locus Clvr can spread to genotype fixation in a constrained area in which all the wildtype copies of the essential gene have been lost (genetic addiction) (as in FIG. 50, 12.5% recombination). But, when spread in space is not constrained, the ultimate loss of Cas9 through segregation and loss in dead individuals who lack functional copies of the essential gene results in loss of drive potential.

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1. A two-vector system comprising: a first vector comprising: a first sequence encoding a first component of a DNA sequence modifying complex; a second sequence encoding a second component of the DNA sequence modifying complex; a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex, a second promoter operably linked to the second sequence encoding the second component of the DNA sequence modifying complex, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene; a second vector comprising: a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.
 2. A two-vector system comprising: a first vector comprising: a first sequence encoding a first component of a DNA sequence modifying complex, a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences; a second vector comprising: a second sequence encoding a second component of the DNA sequence modifying complex; a second promoter operably linked to the second component of the DNA sequence modifying complex, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene.
 3. The two vector system of claim 2, wherein the first vector comprises the second sequence encoding the second component of the DNA sequence modifying complex, and the second vector comprises the first sequence encoding the first component of a DNA sequence modifying complex.
 4. A two-vector system comprising: a first vector comprising: a DNA sequence modifying enzyme; a first promoter operably linked to the DNA sequence modifying enzyme, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene; a second vector comprising: a rescue transgene sequence; a rescue transgene promoter operably linked to the rescue transgene sequence; and optionally, one or more cargo sequences.
 5. The two-vector system of claim 1, wherein the two vectors are configured to be positioned on a single chromosome or a single extrachromosomal element at a distance from each other, on two different chromosomes, a chromosome and an extrachromosomal element, or two different extrachromosomal elements.
 6. The two-vector system of claim 5, wherein the distance between the two vectors is less than 50 map units.
 7. The two-vector system of claim 1, wherein the first component of the DNA sequence modifying complex is a nuclease, a base editor, or a Search and Replace Prime editor.
 8. The two-vector system of claim 7, wherein the nuclease cleaves and generates one or more double strand breaks in the endogenous copy of the essential gene.
 9. The two-vector system of claim 7, wherein the one or more double strand breaks are repaired to create an altered sequence of the essential gene.
 10. The two-vector system of claim 7, Wherein the base editor creates one or more base changes in endogenous copy of the essential gene to create an altered sequence of the essential gene.
 11. The two-vector system of claim 10, wherein the one or more base changes comprise one or more point mutations in the endogenous copy of the essential gene.
 12. The two vector system of claim 7, wherein the Search and Replace Prime editor creates one or more base changes, or insertions or deletions, in the endogenous copy of the essential gene to create an altered sequence of the essential gene.
 13. The two-vector system of claim 1, wherein the rescue transgene is either a recoded copy of the essential gene or is a gene of unrelated sequence, wherein the rescue transgene encodes a protein that is functionally equivalent to a protein encoded by the essential gene, and wherein the DNA sequence modifying enzyme does not modify the rescue transgene.
 14. The two-vector system of claim 1, wherein the chromosome is an autosome, X chromosome, Y chromosome, Z chromosome, W chromosome, a prokaryotic genome, or supernumerary chromosome.
 15. (canceled)
 16. The two-vector system of claim 1, wherein the one or more cargo sequences comprise a one or more foreign gene sequences, or one or more alleles of an endogenous chromosomal or extra-chromosomal gene to which one of the vectors has been linked through nearby, or internal to the gene, insertion on the chromosome or extra-chromosomal element that carries the endogenous allele of interest.
 17. The two-vector system of claim 1, wherein the first, second and rescue transgene promoters are selected from the group consisting of a germline promoter, a male specific germline promoter, a female specific germline promoter, a cell-type specific promoter, a tissue-specific promoter, a Ubiquitous promoter, a promoter activated at a specific stage of mitosis, a promoter activated at a specific stage of meiosis, a viral promoter or prokaryotic promoter.
 18. A method of reversibly modifying a population, the method comprising: obtaining a wild type organism, positioning a two-vector system in the wild type organism generating an altered organism by inducing one or more sequence modifications in an essential gene by a DNA sequence modifying complex in the two-vector system that result in a defect in survival, growth control, fertility, or differentiation in one or more cells in the organism, and rescuing the defect in survival, growth control, fertility, or differentiation by a rescue transgene in the two-vector system, introducing the altered organism in an environment wherein an increase in a frequency of the altered organism is desired relative to a frequency of the wild type organism in a population; replacing the wild type organism with the altered organism in the population in the environment, thereby obtaining a modified population reintroducing the wild type organism in an environment wherein an increase in a frequency of the wild type organism is desired relative to a frequency of the altered organism in the modified population; replacing the altered organism with the wild type organism in the modified population in the environment, thereby reversibly modifying the population.
 19. (canceled)
 20. (canceled)
 21. (canceled)
 22. The method of claim 18, wherein the reversible modification of the population occurs at a rapid rate, high frequency, or both.
 23. The method of claim 22, wherein the rapid rate is defined as replacement of at least 90% of the wild type organism by the altered organism or vice versa in the population after at most 100 generations.
 24. The method of claim 22, wherein the high frequency is defined as replacement of at least 90% of the wild type organism by the altered organism or vice versa after 100 generations in the population.
 25. (canceled)
 26. (canceled)
 27. A two-vector system comprising: a first vector comprising: a first sequence encoding a first component of a DNA sequence modifying complex, a first promoter operably linked to the first sequence encoding the first component of the DNA sequence modifying complex a rescue transgene sequence; a promoter operably linked to the rescue transgene that requires binding by the DNA sequence modifying complex for transcription of the rescue transgene; and optionally, one or more cargo sequences; a second vector comprising: a second sequence encoding a second component of the DNA sequence modifying complex; a second promoter operably linked to the second component of the DNA sequence modifying complex, wherein the DNA modifying enzyme complex modifies an endogenous copy of an essential gene.
 28. The two vector system of claim 1, wherein the first vector comprises the second sequence encoding the second component of the DNA sequence modifying complex, and the second vector comprises the first sequence encoding the first component of a DNA sequence modifying complex.
 29. The two-vector system of claim 1, wherein the two components of the DNA sequence modifying complex, or a single component DNA sequence modifying enzyme, is a nuclease, a base editor, or a Search and Replace Prime editor. 